updated ZFS measurements for ZFS on Linux version 0.7.1

[richardelling]

Required for all PRs:

• [ x] Signed CLA.
• [ x] Associated README.md updated.
• [ x] Has appropriate unit tests.

[danielnelson]

I know this has some overlap with #2623, @tomtastic can you review?

[tomtastic]

@danielnelson As this PR includes the zil stats collection, I'm happy for it to replace #2623, but the checks are failing, can't tell why from looking at the circleci details, @richardelling are all your unit tests OK ?

$CIRCLE_BRANCH: pull/3565
Executing 'mv /home/ubuntu/telegraf /home/ubuntu/telegraf-build/src/github.com/influxdata'
Executing 'cd /home/ubuntu/telegraf-build/src/github.com/influxdata/telegraf'
run 'go fmt ./...' to format your source code.

bash scripts/circle-test.sh returned exit code 1

[richardelling]

@tomtastic my unit tests pass, but it seems the CI fails on pull from my repo?

IMHO, this PR can replace #2623 and there are more stats in the pipeline. I'll be happy to collaborate.

[tomtastic]

No need to collaborate @richardelling, unless you can fix my zpool unit tests for issue #2616? 😁
@danielnelson can you close / cancel #2623 ?