Apply getImeControlTarget() only for IME insets

On an external display, getImeControlTarget returns the remote control
target of the defaul display. This is not desirable for non-IME insets.

Test: dumpsys and check the control target on external display.
Bug: 184325245
Change-Id: I79ee5caacb91d828e28ddb884cf6b8cbdea64386
Merged-In: I79ee5caacb91d828e28ddb884cf6b8cbdea64386
(cherry picked from commit 4e6fb0bc)