Add the Android SDK to the linux CI and turn on Android tests.

Review Request #3538 - Created March 5, 2016 and submitted

Mateo Rodriguez
10, 937, 2993, 3006, 3012
gmalmquist, jsirois, patricklaw, stuhood

This installs and caches the Android SDK on linux CI
runs. The debug.keystore used to be installed along
with the SDK - but I had to recreate it for the CI.
That directory is cached so it should only run once
or if a layer changes.

The Android tests will now be run in the contrib shard.

In 3531 I maintained the '-a' flag as a way to skip
running Android tests, even now that it is moved to
contrib. I did that because since the OSX CI is not
container based it would have to redownload the entire
SDK each run. So Android tests (and the install-android-sdk
script) are only being run on the Linux CI.

This is all that is left to land: A travis run with just the RB passed at:

Stu Hood
Mateo Rodriguez
Mateo Rodriguez
Mateo Rodriguez
Mateo Rodriguez
Stu Hood
Mateo Rodriguez
Review request changed

Status: Closed (submitted)

Change Summary:

Thanks Stu - submitted as 9f8b510c9607c8c33b105a9ca61419c59d04104e