PassphraseRequiredMixin might check for a bound service at a time where
the bind has been requested but the service connection has not been
established yet, and therefore fail to call unbindService, leading to a
leaked service connection. This fixes#1518.
The current activity needs to be finished before calling startActivity.
Otherwise, activities with launchMode singleTask (ConversationListActivity)
will receive a new Intent instead of getting restarted. And in response
to the new Intent, they will run onResume once again and trigger a second restart.
Fixes#1292
