Don't finish resolver activity onStop if it is for home intent

Helps avoid a continuous launch cycle if a resolver activity resolving
the home intent is the only activity in the system and the lock screen
is up which will put the activity in the stopped state. The activity
then finished itself onStop, but is then relaunched by the activity
manager since there are no other activities in the system and the
home activity should be present.

Bug: 27674536
Change-Id: Iaca67a00c4a37f70aafd18aedcbd8dba2f561203