rebuild the unit test suite for synse server

[edaniszewski]

===================================================================== test session starts =====================================================================
platform darwin -- Python 3.6.7, pytest-4.4.1, py-1.8.0, pluggy-0.9.0
cachedir: .tox/py36/.pytest_cache
rootdir: /Users/edaniszewski/dev/vaporio/synse-server
plugins: mock-1.10.4, metadata-1.8.0, html-1.20.0, cov-2.6.1, asyncio-0.10.0
collected 426 items                                                                                                                                           

tests/unit/test_app.py .
tests/unit/test_cache.py .........................................
tests/unit/test_errors.py ...........
tests/unit/test_log.py ..
tests/unit/test_plugin.py ......................................
tests/unit/test_server.py ....
tests/unit/test_tasks.py .
tests/unit/test_utils.py .............
tests/unit/api/test_http.py ......................................................................................................................................................ssssssssssssssss..................................................................
tests/unit/cmd/test_config.py ....
tests/unit/cmd/test_info.py ..
tests/unit/cmd/test_plugin.py ..........
tests/unit/cmd/test_read.py ................
tests/unit/cmd/test_scan.py ......
tests/unit/cmd/test_tags.py .......
tests/unit/cmd/test_test.py .
tests/unit/cmd/test_transaction.py .........
tests/unit/cmd/test_version.py .
tests/unit/cmd/test_write.py ..........
tests/unit/discovery/test_kubernetes.py ...............

--------------------------------- generated html file: /Users/edaniszewski/dev/vaporio/synse-server/results/pytest/index.html ---------------------------------

---------- coverage: platform darwin, python 3.6.7-final-0 -----------
Name                                   Stmts   Miss  Cover
----------------------------------------------------------
synse_server/__init__.py                   8      0   100%
synse_server/__main__.py                   3      3     0%
synse_server/api/__init__.py               0      0   100%
synse_server/api/http.py                 130     17    87%
synse_server/api/websocket.py              9      6    33%
synse_server/app.py                       12      0   100%
synse_server/cache.py                     74      0   100%
synse_server/cmd/__init__.py              10      0   100%
synse_server/cmd/config.py                 6      0   100%
synse_server/cmd/info.py                  13      0   100%
synse_server/cmd/plugin.py                54      0   100%
synse_server/cmd/read.py                  52      0   100%
synse_server/cmd/scan.py                  28      0   100%
synse_server/cmd/tags.py                  16      0   100%
synse_server/cmd/test.py                   6      0   100%
synse_server/cmd/transaction.py           27      0   100%
synse_server/cmd/version.py                6      0   100%
synse_server/cmd/write.py                 34      0   100%
synse_server/config.py                     3      0   100%
synse_server/discovery/__init__.py         0      0   100%
synse_server/discovery/kubernetes.py      71      1    99%
synse_server/errors.py                    30      0   100%
synse_server/i18n.py                       5      0   100%
synse_server/log.py                       11      0   100%
synse_server/plugin.py                    99      0   100%
synse_server/server.py                    46      0   100%
synse_server/tasks.py                     16      8    50%
synse_server/utils.py                     16      0   100%
----------------------------------------------------------
TOTAL                                    785     35    96%
Coverage HTML written to dir results/coverage

=========================================================== 410 passed, 16 skipped in 2.35 seconds ============================================================
___________________________________________________________________________ summary ___________________________________________________________________________
  py36: commands succeeded
  congratulations :)

This PR rebuilds the entire unit test suite for Synse Server, fixing up a lot of the odd/inconsistent/bad test patterns from before, simplifying things a bit, and vastly expanding the number of tests and coverage. There are two caveats to this test suite right now:

1. The kubnernetes discovery tests were just copied over from v2. Then need some work to get them cleaned up and following better test practices. Will open a separate issue. This will be done post-v3 release as it is non-blocking for other work (unless someone else wants to do it earlier)
2. The tests for the /readcache endpoint are written, but they are all skipped. I have not been able to get the tests working with the existing testing tools. The issue seems to be around sanic's testing support around response streaming. I opened a discussion topic on their help board and will wait for a resolution there before determining what the next steps are.

fixes #220