Process key events only if the event source is not ime

Process key events only if the event source is not ime

In some profiles such as TV, the libscl-ui processes
key events in order to handle remote controller's
Arrows/Select keys. But since the remote controller's
Select key has the same key value with the Enter key,
the Enter key event that was generated by our IME,
could be interpreted as remote controller's Select key.
So, for preventing this case, we are not going to
let libscl-ui to process key events if the key event
was generated by ime itself.

Change-Id: Ia2719f552adebf1e40a42f19dec924c2f9bb3daf