Stabilize Travis-CI builds

[pedrovgs]

As we've seen for the last months Travis-CI is failing constantly due to problems initializing the Android emulator, even when our tests are not flacky at all. Travis-CI is one of the core components in this project, so we should try to stabilize our build in Travis-CI environments using this tool

[voghDev]

👀 I've got my eyes on this issue, as Travis also fails for me due to the same cause

[pedrovgs]

:) thanks @voghDev you can try with https://github.com/linkedin/test-butler if you want!