Document a somewhat peculiar signal behavior mismatch during Bt discovery

Change-Id: I8f9ac85e7753a9d6142bbefcd0e4bcda09e0f3d8
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>
Reset QML Bluetooth discovery model if an error occurred during device discovery

This is due to a behavior difference of the finished() signal between
service and device discovery.

Change-Id: I59d6358171275987f07f86a6da80e8435445fd0e
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>