timob-7842: 'return' event should only fire once when search key is clicked.
timob-7842: fix 2
timob-7842: added a comment to explain the fix:
"This check to prevent 'return' event from being fired twice when return key is hit. In other words, when return key is clicked
this callback is triggered twice: the first time with actionId = EditorInfo.IME_NULL, the 2nd time with the corresponding return key actionId."

Signed-off-by: Hieu Pham <hpham@appcelerator.com>