Buck doesn't print out the error messages for failing Go tests

Created by: linzhp

A typical message for failed Go tests looks like this

TESTING //:test-failure
BUILT 19/19 JOBS 0.0s //:test-failure
FAIL    <100ms  0 Passed   0 Skipped   1 Failed   //:test-failure
FAILURE go_test TestAdd2: 

====STANDARD OUT====

====STANDARD ERR====

TESTS FAILED: 1 FAILURE
Failed target: //:test-failure
FAIL //:test-failure

The standard output and error are both empty. This commit can help reproducing the issue