Return if user try to open clipboard window again during clipboard is showing

Return if user try to open clipboard window again during clipboard is showing

[Title] Return if user try to open clipboard window again during clipboard is showing
[Issue#] N/A
[Problem] Try to open clipboard even if while clipboard is opening few times. after then try to paste by clipboard then many of items are pasted
[Cause] Callbacks are registed when clipboard is opened. before close clipboard window callbacks are not delete.
[Solution] Return if user try to open clipboard window again during clipboard is showing

Change-Id: I8904def2daece8b1d0aa3ebbb2686e71ef9c251c