MEDIUM: stream-int: completely remove stream_int_update_embedded()

MEDIUM: stream-int: completely remove stream_int_update_embedded()

This one is not needed anymore as what it used to do is either
completely covered by the new stream_int_notify() function, or undesired
and inherited from the past as a side effect of introducing the
connections.

This update is theorically never called since it's assigned only when
nothing is connected to the stream interface. However a test has been
added to si_update() to stay safe if some foreign code decides to call
si_update() in unsafe situations.