Fix 6283709: set max FUL failed attempts to 5

After an unrecognized face occurs 5 times in a row, we disable FUL
until the user unlocks via the backup lock.  This prevents attacks
where someone tries a bunch of different photos, hoping for a good
enough match to the device's owner.

This value was previously set to 15, which is much higher than
necessary.  This change sets it to 5.  We've been holding off on
this change because it makes our testing more difficult, but we
want this in there for factory ROM this week.

Change-Id: I4e1acc5b1dcc2c0629e0c0fe97a837d6edc44d5d