Properly deal with pairing errors in btfiletransfer example

Pairing error signals were ignored which lead to a situation in which
the UI remained in the "attempting to pair" state.

Change-Id: I66f8855cf5ab72d608650b36a844c53e27624452
Reviewed-by: Oleg Shparber <trollixx@gmail.com>
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>