monitor: let mon_list be tail queue

It was QLIST.  I want to use this list to do monitor priority job later,
which need tail insertion ability.  So switching to a tail queue.
Reviewed-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180309090006.10018-9-peterx@redhat.com>
Signed-off-by: NEric Blake <eblake@redhat.com>

monitor.c

@@ -207,7 +207,7 @@ struct Monitor {
     void *password_opaque;
     mon_cmd_t *cmd_table;
     QLIST_HEAD(,mon_fd_t) fds;
-    QLIST_ENTRY(Monitor) entry;
+    QTAILQ_ENTRY(Monitor) entry;
 };
 
 /* QMP checker flags */
@@ -216,7 +216,7 @@ struct Monitor {
 /* Protects mon_list, monitor_event_state.  */
 static QemuMutex monitor_lock;
 
-static QLIST_HEAD(mon_list, Monitor) mon_list;
+static QTAILQ_HEAD(mon_list, Monitor) mon_list;
 static QLIST_HEAD(mon_fdsets, MonFdset) mon_fdsets;
 static int mon_refcount;
 
@@ -417,7 +417,7 @@ static void monitor_qapi_event_emit(QAPIEvent event, QDict *qdict)
     Monitor *mon;
 
     trace_monitor_protocol_event_emit(event, qdict);
-    QLIST_FOREACH(mon, &mon_list, entry) {
+    QTAILQ_FOREACH(mon, &mon_list, entry) {
         if (monitor_is_qmp(mon)
             && mon->qmp.commands != &qmp_cap_negotiation_commands) {
             monitor_json_emitter(mon, QOBJECT(qdict));
@@ -4063,7 +4063,7 @@ void monitor_init(Chardev *chr, int flags)
     }
 
     qemu_mutex_lock(&monitor_lock);
-    QLIST_INSERT_HEAD(&mon_list, mon, entry);
+    QTAILQ_INSERT_HEAD(&mon_list, mon, entry);
     qemu_mutex_unlock(&monitor_lock);
 }
 
@@ -4072,8 +4072,8 @@ void monitor_cleanup(void)
     Monitor *mon, *next;
 
     qemu_mutex_lock(&monitor_lock);
-    QLIST_FOREACH_SAFE(mon, &mon_list, entry, next) {
-        QLIST_REMOVE(mon, entry);
+    QTAILQ_FOREACH_SAFE(mon, &mon_list, entry, next) {
+        QTAILQ_REMOVE(&mon_list, mon, entry);
         monitor_data_destroy(mon);
         g_free(mon);
     }