Add capability to run specific unit test(s)

Prior to this changeset, running "make unit-tests"
will execute go tests for all Fabric packages.
This changeset adds the ability to selectively run
go tests for specified packages while still using
the build environment (which is useful to emulate
what is run in CI).  To do this, the following
changes were made:

- Added TEST_PKGS environment variable to
unit-tests/run.sh.  If not set, you default
to running tests for all packages

- Modified unit-test/docker-compose.yaml to
pass TEST_PKGS into the Docker build env

TEST_PKGS expects a space-delimited list of
qualified Go pkg URLs like you would pass to
the go list command.

To use the new feature, export / set TEST_PKGS
prior to running make unit-tests :

export TEST_PKGS=\
"github.com/hyperledger/fabric/core/comm/... \
github.com/hyperledger/fabric/gossip/..."
make unit-tests

*latest patch uses a shorter syntax in run.sh

Fixes FAB-1455

Change-Id: I5d889f3f25ad3b628c463202939638ba6906d85f
Signed-off-by: Gari Singh <gari.r.singh@gmail.com>

unit-test/docker-compose.yml

@@ -16,6 +16,7 @@ unit-tests:
     - UNIT_TEST_PEER_IP=vp
     - GO_LDFLAGS
     - OUTPUT
+    - TEST_PKGS=${TEST_PKGS}
   volumes:
     - /var/run/docker.sock:/var/run/docker.sock
     - ${GOPATH}/src/github.com/hyperledger/fabric:/opt/gopath/src/github.com/hyperledger/fabric

unit-test/run.sh

@@ -3,9 +3,12 @@
 set -e
 ARCH=`uname -m`
 
-echo -n "Obtaining list of tests to run.."
+#check to see if TEST_PKGS is set else use default (all packages)
+TEST_PKGS=${TEST_PKGS:-github.com/hyperledger/fabric/...}
+echo -n "Obtaining list of tests to run for the following packages: ${TEST_PKGS}"
+
 # Some examples don't play nice with `go test`
-PKGS=`go list github.com/hyperledger/fabric/... 2> /dev/null | \
+PKGS=`go list ${TEST_PKGS} 2> /dev/null | \
                                                   grep -v /vendor/ | \
                                                   grep -v /build/ | \
 	                                          grep -v /examples/chaincode/chaintool/ | \