Initialize new intermission infokey at map load

Set infokey intermission to default off.

src/world.qc

@@ -178,6 +178,8 @@ void() worldspawn =
 		cvar_set ("sv_gravity", "800");
 	}
 
+	forceinfokey (world, "intermission","off");
+
 	// the area based ambient sounds MUST be the first precache_sounds
 
 	// player precaches