fix: terminate connection on connect failure to prevent socket leak

Author: Adamkadaban

nxc/protocols/rdp.py

@@ -590,6 +590,7 @@ async def execute_shell(self, payload, get_output, shell_type):
             await self.connect_rdp()
         except Exception as e:
             self.logger.debug(f"Error connecting to RDP: {e!s}")
+            await self.terminate_conn()
             return None
 
         try: