Switch to Enforcers bloody skin when he's killed

When killing the enforcer with one shot (instead of damaging him first
without killing, which will switch to the bloody skin), the skin wasn't
changed. Now it is.

src/monster/infantry/infantry.c

@@ -504,6 +504,7 @@ infantry_die(edict_t *self, edict_t *inflictor /* unused */,
 	/* regular death */
 	self->deadflag = DEAD_DEAD;
 	self->takedamage = DAMAGE_YES;
+	self->s.skinnum = 1; /* switch to bloody skin */
 
 	n = rand() % 3;