Investigate and fix Elasticsearch test failures

[jpkrohling]

See #43 : although the PR had nothing to do with ES, the tests were not passing. The tests are probably failing intermittently and need to be fixed.

[pavolloffay]

This https://travis-ci.org/jaegertracing/jaeger-kubernetes/builds/284229897?utm_source=github_status&utm_medium=notification failed also.

[pavolloffay]

#50 fixed some issues, but ES tests are still not stable. Locally they pass always so the problem is with travis environment.

[jpkrohling]

I'm closing this one, as I haven't seen these intermittent failures in a while. Please, reopen if this is still relevant.