Change the state of EventData to EDITING in RemoveText

- Currently, in certain cases, even if Backspace key is pressed
 after cursor blink is stopped, cursor blink does not restart and
 the cursor is also not shown.

- It means, after EventData is changed to INACTIVE state due to
 KeyboardFocusLostEvent(), StopCursorBlink() is called.
  After that, in RemoveText(), which is called in Backspace key,
 EventData cannot be changed to EDITING state and StartCursorBlink() is not called.
  On the other hand, when the character commits or the arrow keys are pressed,
 EventData is changed to EDITING state and the cursor is displayed on screen.

- So, added 'ChangeState( EventData::EDITING )' when the state is INACTIVE.

Change-Id: Ib79dfdc6f7308d084772f62dc49918a694cfc438
Signed-off-by: Seoyeon Kim <seoyeon2.kim@samsung.com>