[gstreamer] Always start camera in image mode. Fixes JB#8036
[gstreamer] Always start camera in image mode. Fixes JB#8036

Android hal on qualcomm doesn't like it. Viewfinder will freeze and
the errors below are seen in the log:
E/mm-camera( 1423): mctl_pp_dest_divert Frame diverted in camera mode. Sending back.

sailfishos/gst-droidcamsrc,sailfishos/gst-droidcamsrc,sailfishos/gst-droidcamsrc