Fix InputConnection creation callback

As noted in the linked bug, in certain scenarios IC established callback
is not always called. As a fix, we make sure we don't return early when
MSG_BIND callback is received from IME

Fix: 228105257
Bug: 217971553

Test: atest StylusHandwritingTest#testHandwritingEndToEnd

Change-Id: I780327003f7145c4f9b9df4dc5243227d7e67d92