MEDIUM: stream: Save SC and channel flags earlier in process_steam()

MEDIUM: stream: Save SC and channel flags earlier in process_steam()

At the begining of process_stream(), the flags of the stream connectors and
channels are saved to be able to handle changes performed in sub-functions
(for instance in analyzers). But, some operations were performed before
saving these flags: Synchronous receives and forced shutdowns. While it
seems to safe for now, it is a bit annoying because some events could be
missed.

So, to avoid bugs in the future, the channels and stream connectors flags
are now really saved before any other processing.