If the driver requires more data, just unref the frame at the moment
then retreive/finish the frame after encoding is finished.
This also fixes a memory leak.
https://bugzilla.gnome.org/show_bug.cgi?id=790312
Set the pts and dts on the frame that we receive from the msdk.
Also fix the inverted logic in setting sync points, previously we
were marking all frames as sync points except IDRs.
https://bugzilla.gnome.org/show_bug.cgi?id=782801