tests/icles/dccp: Release reference to parent

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=732977
camerabin2: Flush downstream after setting src to READY

v4l2src requires all buffers to come back in order to cleanly stop
streaming. Flushing the pipline should force all buffers to come
back.

https://bugzilla.gnome.org/show_bug.cgi?id=732741