Refactored setOrientation() for Android.

Appium throws "Set the orientation, but app refused to rotate." when
setting the orientation to landscape on Android, which was fixed by
calling the correct function. Also, made the code simpler by defining
portrait=(0 degree rotation) and landscape=(270 degree rotation)
regardless of current display rotation. Moreover, unfreeze device
rotation at the end.
Merge pull request #1260 from paymand/orientation_refactor

Refactored setOrientation() for Android.