将保活请求由OPTIONS改为GET_PARAMETER（来自VLC保活参考）

client.go

@@ -309,7 +309,7 @@ func (client *RTSP) startStream() {
 			headers := make(map[string]string)
 			headers["Require"] = "implicit-play"
 			// An OPTIONS request returns the request types the server will accept.
-			if err := client.RequestNoResp("OPTIONS", headers); err != nil {
+			if err := client.RequestNoResp("GET_PARAMETER", headers); err != nil {
 				// ignore...
 			}
 		}