fix Samsung real devices login hang problem

Tests hang on login, for specific Samsung devices, currently could be repro in S3/S5
Other real devices like Nexus, and S3/S5 in emulators works fine.

The problem is Samsung has a different MultiPhoneWindow support, while Selendroid doesn't support.

I didn't find src from Samsung yet, and official android src doesn't contain that, but my debugging experience and this issue from robotium might be able to confirm this: https://code.google.com/p/robotium/issues/detail?id=600