Memory leak in IInputMethodSessionWrapper executeMessage

In some cases the executeMessage is called with
mInputMethodSession == null. For the messages

DO_UPDATE_SELECTION, DO_APP_PRIVATE_COMMAND

memory is leaked. This commit recycles the args freeing
the allocated memory.

Change-Id: Ic5455a993442780d43a3b0b02e84a7ab931010b1
Merge "Memory leak in IInputMethodSessionWrapper executeMessage" into kitkat