Fix unexpected IME switcher dialog hidden

Previous CL[1] gives a wrong signal for IMMS might thought the IME
surface parent has changed by transfering to the new IME control
target, but actually that signal mixtured the forcing IME parent
flag, so IME switcher dialog may hidden in such misleading way.

Also, in WM didn't consider the control change might related
to the app is relaunching case, and it's the intermediate state we
should not report to IMMS for this misleading control changed signal.
(i.e. in WindowState#removeImmediately, if the window is during
relaunching and we should not set null IME input target to affect
DC#updateImeParent)

[1]: Iae3dd713b1e980067d28debea4e0a03707aa7938

Fix: 224998014
Fix: 215448483
Fix: 227553661
Test: manul as below steps:
1)  Installed alternate keyboard app (swift keyboard).
2). From all apps > Tap on search > Keyboard pops up
    > Swipe up navigation to exit all apps.
3). From all apps > Open Settings > Tap on Search > Keyboard pops up
    > Tap on switch input button on navigation and observing.
4). Expect IME switcher dialog should be shown and not be dismissed.

Change-Id: Ib0813e2c12909ede4e582eb3499599e3cc253490