rtsp: clear the entire builder structure

And use structure instead of variable with sizeof when
clearing the rtsp message structure, for clarity.

gst-libs/gst/rtsp/gstrtspconnection.c

@@ -239,7 +239,7 @@ static void
 build_reset (GstRTSPBuilder * builder)
 {
   g_free (builder->body_data);
-  memset (builder, 0, sizeof (builder));
+  memset (builder, 0, sizeof (GstRTSPBuilder));
 }
 
 /**

gst-libs/gst/rtsp/gstrtspmessage.c

@@ -463,7 +463,7 @@ gst_rtsp_message_unset (GstRTSPMessage * msg)
   }
   g_free (msg->body);
 
-  memset (msg, 0, sizeof *msg);
+  memset (msg, 0, sizeof (GstRTSPMessage));
 
   return GST_RTSP_OK;
 }