Try to dismiss Keyguard bypassing bouncer only for active users

Some bouncers might allow showing keyguards for users that are not
currently active (e.g. before any user is signed in, in which case the
system user is active). Make sure that keyguard is not dismissed
without showing bouncer in these cases.

Change-Id: I0e037b2d4e095d49c1f0d06a9fe1b9a6233421b0
(cherry picked from commit aa69fd41)