Fix iPhone crash when source is switched

The error message that is thrown in the device console is “mobile
safari An AVPlayerItem cannot be associated with more than one instance
of AVPlayer”
#FEC-1293 #message Fix mobile safari crash  on postroll done

1. Prevent crash on mobile safari on post roll done
2. Suppress full screen toggling between media end and post roll
Suppress events on pre-sequence

When playing pre/post rolls on a player that doesn’t support video
siblings the events from the pre/post rolls are fired and handled by
the original player.
This causes unexpected behaviour to occur on second play and onwards.
#SUP-2287 #comment Fix browser crash when stopping while ad plays #time 2d
Merge pull request #709 from kaltura/FEC-1293

Support mobile safari ad display