`emacsclient` started with `-c` or `-t` argument create a new frame that shall
not be used to manage X windows.
Also fix some related input focus issues (with some remaining unfixed).
Close#17.
* Make sure `exwm-manage--manage-window-queue` is cleaned
* Improve input focus handling after unmanaging a window
* Remove a redundant call to `exwm-layout--show`