Fix Travis run on Mac

[garrettjonesgoogle]

The build of google-cloud-java is consistently failing on Mac:

$ git clone -b travis `git config --get remote.origin.url` target/travis
Cloning into 'target/travis'...
error: RPC failed; curl 56 SSLRead() return error -36
fatal: The remote end hung up unexpectedly
fatal: early EOF
fatal: index-pack failed

This should be fixed.

[michaelbausor]

The error shown above can be fixed/mitigated using travis_retry, as per this PR: #2384

However, this is not the only cause of build failure on OSX. So far I have identified that the Spanner suite seems to be the cause of the problem, but have not found a more specific reason yet.

[michaelbausor]

See below for the truncated output of a failed Travis build on OSX. The build appears to hang after the Spanner SessionPoolStressTest. The next test is the SessionPoolTest.

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Concurrency config is parallel='none', perCoreThreadCount=true, threadCount=2, useUnlimitedThreads=false
Running com.google.cloud.spanner.AbstractStructReaderTypesTest
Tests run: 72, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.841 sec
Running com.google.cloud.spanner.DatabaseAdminClientImplTest
Tests run: 7, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.411 sec
Running com.google.cloud.spanner.DatabaseIdTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.007 sec
Running com.google.cloud.spanner.DatabaseTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.01 sec
Running com.google.cloud.spanner.GrpcResultSetTest
Tests run: 23, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.416 sec
Running com.google.cloud.spanner.InstanceAdminClientImplTest
Tests run: 7, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.102 sec
Running com.google.cloud.spanner.InstanceConfigIdTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.004 sec
Running com.google.cloud.spanner.InstanceIdTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.024 sec
Running com.google.cloud.spanner.InstanceTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.056 sec
Running com.google.cloud.spanner.KeyRangeTest
Tests run: 7, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.047 sec
Running com.google.cloud.spanner.KeySetTest
Tests run: 24, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.055 sec
Running com.google.cloud.spanner.KeyTest
Tests run: 6, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.034 sec
Running com.google.cloud.spanner.MutationTest
Tests run: 23, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.133 sec
Running com.google.cloud.spanner.OperationTest
Tests run: 6, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.041 sec
Running com.google.cloud.spanner.OptionsTest
Tests run: 6, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.011 sec
Running com.google.cloud.spanner.ReadFormatTest
Tests run: 15, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.118 sec
Running com.google.cloud.spanner.ResultSetsTest
Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.016 sec
Running com.google.cloud.spanner.ResumableStreamIteratorTest
Tests run: 13, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 6.378 sec
Running com.google.cloud.spanner.SessionImplTest
Tests run: 15, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.151 sec
Running com.google.cloud.spanner.SessionPoolOptionsTest
Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.006 sec
Running com.google.cloud.spanner.SessionPoolStressTest
Tests run: 6, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 45.602 sec

No output has been received in the last 10m0s, this potentially indicates a stalled build or something wrong with the build itself.
Check the details on how to adjust your build configuration on: https://docs.travis-ci.com/user/common-build-problems/#Build-times-out-because-no-output-was-received

The build has been terminated

[pongad]

@garrettjonesgoogle We're moving to Circle. Is this still relevant?

[garrettjonesgoogle]

We're moving integration tests to Circle. If we decide to switch unit tests to Circle too, then this would not be relevant any more.