sv_maxidle_playertospectator: fix joining players getting moved to spec immediately

sv_maxidle_playertospectator: fix joining players getting moved to spec immediately

In gametypes without teams, if the player left the welcome dialog open for
the duration of sv_maxidle_playertospectator and then clicked join,
they were immediately moved back to spec for idling.

This could happen with any menu dialog or console command that allowed
joining without changing CSQC button state or mouse angle.

It was not noticeable prior to !1021 because pressing jump to join
changed the player's button state which reset their idlesince.
sv_maxidle_minplayers would have prevented this being found in local testing.