[HOTFIX] Delay main_loop shutdown to avoid deadlock

[HOTFIX] Delay main_loop shutdown to avoid deadlock

When keyboard switches from Tizen Keyboard to WebApp Keyboard,
keyboard select button enables before WebApp keyboard is completely loaded.
In that time if keyboard switches back to Tizen Keyboard,
deadlock occurs between main_loop and Webview.
To avoid this deadlock, delay main_loop until webview load is finished

BUG: http://suprem.sec.samsung.net/jira/browse/TSAM-11361

Change-Id: I469bea8ff1b3dc3bbb69a37f0fe6114f30b8d855
Signed-off-by: ws29.jung <ws29.jung@samsung.com>