Check if BT is already enabled before starting activity.

If BT is off, and if the user sends a file, BT will be turned on
and the "Enabling dialog" wil be shown. But with the hot feature,
BT turns on very fast which leads to the intent being missed and the
enabling dialog not being dismissed.

Change-Id: I4f4a6f08e04922a61eb7138b76383a77f8d37da4