Fix admin pause control by disabling it

I wanted to make the native YouTube "pause" control work in the
following way:
 - non-admins press pause, and they unset "intendToSync" and pause.
 - admins press pause, and it functions as "Pause for All", sending a
   pause signal to all participants.
However, the YouTube onPlayerStateChange API doesn't distinguish pause
button presses from other events that result in a "pause" -- including
seeks, buffering, etc.  I could find no way to reliably distinguish
pause button-presses for other actions.

So: for admins, the "pause" button now results in a temporary hiccup --
the player will re-sync on the next control signal and begin playing
again.  Essentially, pause is "disabled" for admins when "intendToSync"
is set.