Fix IME insets animation applies again when restartInput called

Since previously mShowRequested will never set as false once
the first showSoftInput calls, unless hideSoftInput be called,

As new insets feature enabled, showSoftInput will always apply insets
animation, that will have a problem that when the app calls restartInput to
re-create input method session, showCurrentInputLocked will be called
and IME insets animation will be applied again.

Set mShowRequested as false when showSoftInput has done.

Fix: 153026470
Test: atest CtsInputMethodTestCases
Change-Id: Ia1ceb8e0e939376eb1d387c864aecd88504f3126