Fix up output for test suites that are filtered out

[jacobsa]

Currently there's a bunch of extra junk printed. For example:

Hausdorff: [~/go/clients/src/github.com/jacobsa/oglemock]$ go test --ogletest.run=ReturnTest
warning: building out-of-date packages:
    github.com/jacobsa/oglemock/sample/mock_io
installing these packages with 'go install' will speed future tests.

ok      github.com/jacobsa/oglemock 0.016s
[----------] Running tests from ControllerTest
[----------] Finished with tests from ControllerTest
[----------] Running tests from IntegrationTest
[----------] Finished with tests from IntegrationTest
[----------] Running tests from InternalExpectationTest
[----------] Finished with tests from InternalExpectationTest
[----------] Running tests from ReturnTest
[ RUN      ] ReturnTest.EmptySet
[       OK ] ReturnTest.EmptySet
[ RUN      ] ReturnTest.MultipleValues
[       OK ] ReturnTest.MultipleValues
[ RUN      ] ReturnTest.OneValue
[       OK ] ReturnTest.OneValue
[----------] Finished with tests from ReturnTest
PASS