Test CI config: showcase 'adb devices; sleep 10' trick and test new error 137

Add 'adb wait-for-device' and 'sleep 10' after adb wait-for-device

adb devices:
Prints a list of all attached emulator/device instances by serial number and state.

sleep 10:
After resolve the AVD creation/Gradle download conflict, Travis kills jobs when
exists concurrency between emulator boot and android dependencies downloads.

This is only a test to be reverted after improve CI configuration file.