modules/chanserv/close: check correct flags variable for log target

modules/chanserv/close: check correct flags variable for log target

A user reported that the ChanServ CLOSE command was not working for
their channel, saying that the channel could not be closed.

MC_HOLD and CHAN_LOG both have the same value (1), but the former is
for flags in `struct mychan`, and the latter is for `struct channel`.

This lead me to believe that the channel was defined as a log target,
when in reality it was checking the wrong flags field and deducing
that the channel was a log target because it was held.

Check the correct flags field.

Reported-by: @hello-smile6