At the moment `subnet` is an alias of `subnet_id`. The way, how aliases work in ansible modules, is that ansible does add intended key to param in case alias is used. When riginal key is used, aliases are not populated. Right now in case user define `subnet_id` instead of its alias `subnet` module will fail with KeyError. Change-Id: I5ce547352097ea821be4c9bbc18147575986c740