Intermittent failure when building frontend integration test.

[xiahome]

Below is the failure message.

:ambry-frontend:processUnitTestResources UP-TO-DATE
:ambry-frontend:unitTestClasses
:ambry-frontend:unitTest
com.github.ambry.frontend.FrontendIntegrationTest > multipartPostGetHeadTest[3] FAILED
    java.lang.NullPointerException
        at com.github.ambry.frontend.FrontendIntegrationTest.getBlobInfoAndVerify(FrontendIntegrationTest.java:576)
        at com.github.ambry.frontend.FrontendIntegrationTest.doPostGetHeadDeleteTest(FrontendIntegrationTest.java:388)
        at com.github.ambry.frontend.FrontendIntegrationTest.multipartPostGetHeadTest(FrontendIntegrationTest.java:191)
74 tests completed, 1 failed
:ambry-frontend:unitTest FAILED
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':ambry-frontend:unitTest'.
> There were failing tests. See the report at: file:///home/travis/build/linkedin/ambry/ambry-frontend/build/reports/tests/index.html
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
BUILD FAILED
Total time: 49.581 secs
The command "./gradlew build && ./gradlew codeCoverageReport" exited with 1.
before_cache.1
0.00s$ rm -f  $HOME/.gradle/caches/modules-2/modules-2.lock
before_cache.2
0.00s$ rm -fr $HOME/.gradle/caches/*/plugin-resolution/
cache.2
store build cache
0.00s
1.42snothing changed, not updating cache
Done. Your build exited with 1.