fix nxos_banner (#34695)

Signed-off-by: Trishna Guha <trishnaguha17@gmail.com>

lib/ansible/modules/network/nxos/nxos_banner.py

@@ -115,6 +115,8 @@ def map_config_to_obj(module):
     if "Invalid command" in output:
         module.fail_json(msg="banner: exec may not be supported on this platform.  Possible values are : exec | motd")
 
+    if isinstance(output, dict):
+        output = list(output.values())[0]
         if isinstance(output, dict):
             output = list(output.values())[0]