qdev-monitor: Unref device when device_add fails

qdev_device_add() leaks the created device upon failure.  I suspect this
problem crept in because qdev_free() unparents the device but does not
drop a reference - confusing name.

Cc: qemu-stable@nongnu.org
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NAndreas Färber <afaerber@suse.de>

qdev-monitor.c

@@ -527,6 +527,7 @@ DeviceState *qdev_device_add(QemuOpts *opts)
     }
     if (qemu_opt_foreach(opts, set_property, qdev, 1) != 0) {
         qdev_free(qdev);
+        object_unref(OBJECT(qdev));
         return NULL;
     }
     if (qdev->id) {
@@ -540,6 +541,7 @@ DeviceState *qdev_device_add(QemuOpts *opts)
         g_free(name);
     }        
     if (qdev_init(qdev) < 0) {
+        object_unref(OBJECT(qdev));
         qerror_report(QERR_DEVICE_INIT_FAILED, driver);
         return NULL;
     }