Fingerprint: do not error out when stopping to listen

 * when stopListening gets called, we cancel via the cancellation signal,
   which calls the onAuthenticationError callback.

 * detect if we are canceling and do not execute the error code

 * fixes the finger print icon hiding when closing the LockPatternActivity,
   which causes the lock pattern to resize

TICKET: RM-208
Change-Id: I5bb62064f885b67836bd78af854cca950c3401fa
Signed-off-by: Alexander Martinz <eviscerationls@gmail.com>