fix punching task leak (#298)

the punching task creator doesn't check if the task is already
running, and may create many punching task to same peer node.

this patch also improve hole punching by checking hole punch packet
even if punch rpc is failed.

easytier-gui/src-tauri/src/lib.rs

@@ -136,7 +136,7 @@ impl NetworkConfig {
         }
 
         cfg.set_rpc_portal(
-            format!("127.0.0.1:{}", self.rpc_port)
+            format!("0.0.0.0:{}", self.rpc_port)
                 .parse()
                 .with_context(|| format!("failed to parse rpc portal port: {}", self.rpc_port))?,
         );