Dont fire user_joined_room when guest hits /events
Dont fire user_joined_room when guest hits /events

Firing the 'user_joined_room' signal everytime a guest hits /events
causes all presence for that room to be returned in the stream. This may
sound helpful, but causes clients to tightloop calling /events.

In general, guest users should get the initial presence from (room)
intial sync and so we don't require presence to sbsequently come down
the event stream.

matrix-org/synapse,matrix-org/synapse,matrix-org/synapse,TribeMedia/synapse,TribeMedia/synapse,TribeMedia/synapse,matrix-org/synapse,matrix-org/synapse,matrix-org/synapse,TribeMedia/synapse,TribeMedia/synapse