Fix transport getting set to None when not set explicitly (#24769)

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

lib/ansible/module_utils/nxos.py

@@ -56,6 +56,7 @@ nxos_argument_spec = {
 
 # Add argument's default value here
 ARGS_DEFAULT_VALUE = {
+    'transport': 'cli',
     'timeout': 10
 }