monitor: use QEMU_LOCK_GUARD a bit more

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

monitor/monitor.c

@@ -161,10 +161,9 @@ static gboolean monitor_unblocked(void *do_not_use, GIOCondition cond,
 {
     Monitor *mon = opaque;
 
-    qemu_mutex_lock(&mon->mon_lock);
+    QEMU_LOCK_GUARD(&mon->mon_lock);
     mon->out_watch = 0;
     monitor_flush_locked(mon);
-    qemu_mutex_unlock(&mon->mon_lock);
     return FALSE;
 }
 
@@ -203,9 +202,8 @@ static void monitor_flush_locked(Monitor *mon)
 
 void monitor_flush(Monitor *mon)
 {
-    qemu_mutex_lock(&mon->mon_lock);
+    QEMU_LOCK_GUARD(&mon->mon_lock);
     monitor_flush_locked(mon);
-    qemu_mutex_unlock(&mon->mon_lock);
 }
 
 /* flush at every end of line */