Fix input window commands

There were two fixes here:
1. InputWindowCommands were getting merged from
pendingInputWindowCommands. This caused the old commands to continue
getting applied. Instead inputWindowCommands gets set to
pendingInputWindowCommands.

2. Only set mPendingSyncInputWindows to true if the transaction contains
syncInputWindows. This is to prevent setting mPendingSyncInputWindows to
false while waiting for a callback from InputDispatcher.

Test: WindowInputTests
Fixes: 129087315
Change-Id: I8db30820da9580854ba4d02ee419b5766bd7b24a