Contacts: Fix screen no response when import the .vcf file

It will display "import contacts from vCard" dialog when import .vcf
file from files application. If user click out side of dialog, the
screen will darkens and no response. that is because dialog disappears
but the container doesn't finish.

Make sure dialog can't be canceled when touch out side of dialog. this
behavior is consistent with pixel contacts.

Change-Id: Ibe8c12cc21555de7bee3b93924ec6fd1a7442e07