Fix issue where fast 180 degree landscape rotation is not detected.

- Cleaned up imports in InCallActivity.
- Added new OrientationEventListener to listen for orientation changes
to the device.  This listener returns the current device rotation in
degrees.  Use the windowManager to get the current display rotation (e.g.
in coarse 90 degree, 180, etc).
- This solves the problem - can now detect rotation from landscape to
landscape.

Bug: 20727115
Change-Id: Icfad2b26083bb8236e9f4fe5580e3828cdef11b8