Special modes like +j can be tracked easily just by adding the necessary
code to parse them to set_channel_mlock(). This will cover propagation
as well.
This check sometimes blocks oper overrides (OMODE).
It does not stop any hacks that the channelTS check
already stops, because CHFL_DEOPPED is only set when
this server ignored an @ in an incoming SJOIN (the
SJOIN is then propagated without the @) and this
can only be because of a TS difference.