Fix handling of multiple users on a +h account in the support channel(s).

Fix handling of multiple users on a +h account in the support channel(s).

Do not remove +g from a +h account when one of several users on the
account leave a support channel, which gix reported in SF#2649505.

src/chanserv.c (handle_part): Keep the +g flag if any user on the same
  account is in any support channel.
src/nickserv.c (nickserv_apply_flags): Likewise here, for flag changes.