Remove SET_ORIENTATION_CHANGE_COMPLETE

Because it is equivalent to mOrientationChangeComplete. Also
centralized the writing of mOrientationChangeComplete to
setOrientationChanging so that it is easier to put additional
operation in a single place.

Bug: 178472794
Test: CtsWindowManagerDeviceTestCases
Change-Id: I4882b4bb712c957eefc476c9e582d14adc96f246