QMP: Don't leak on connection close

QMP's chardev event callback doesn't call
json_message_parser_destroy() on CHR_EVENT_CLOSED. As the call
to json_message_parser_init() on CHR_EVENT_OPENED allocates memory,
we'are leaking on close.

Fix that by just calling json_message_parser_destroy() on
CHR_EVENT_CLOSED.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

monitor.c

diff --git a/monitor.c b/monitor.c
index 23c0661..ae125b8 100644
--- a/monitor.c
+++ b/monitor.c
@@ -4404,16 +4404,20 @@
  */
 static void monitor_control_event(void *opaque, int event)
 {
-    if (event == CHR_EVENT_OPENED) {
-        QObject *data;
-        Monitor *mon = opaque;
+    QObject *data;
+    Monitor *mon = opaque;
 
+    switch (event) {
+    case CHR_EVENT_OPENED:
         mon->mc->command_mode = 0;
         json_message_parser_init(&mon->mc->parser, handle_qmp_command);
-
         data = get_qmp_greeting();
         monitor_json_emitter(mon, data);
         qobject_decref(data);
+        break;
+    case CHR_EVENT_CLOSED:
+        json_message_parser_destroy(&mon->mc->parser);
+        break;
     }
 }