cmd: always register server-only commands, don't register client-only commands on...

cmd: always register server-only commands, don't register client-only commands on dedicated server

Fixes the lack of the `heartbeat` command on dedicated and listen, and
the presence of commands like `toggleconsole` on dedicated.

Similar to 3a58ad52e63635c93e95955f984fd6052156e56b this might reveal a
few commands that aren't flagged correctly.

Changes the bitmask vars to the correct type.
Renames cmd_flags to cmd_flagsmask for consistency.

Signed-off-by: bones_was_here <bones_was_here@xonotic.au>