Camera2: Do not issue autofocus cancel if preview stopped

942890667aa08cc3c1305d7ba64c1340df1219db introduced the option to not
issue autofocus cancel if the preview was stopped. Extend it to the case
where the preview is stopped because the camera was called as an intent
(ie from MMS client)

Change-Id: I30032d8375665ecf6be471bf480c1f118d25423b