ios_static_route idempotence fix (#35912)

* Remove default admin_distance and fix the idempotence thereof

Fixes #33290

* Fix tests and use yaml anchors to shorten tests

* Add test for undefined admin_distance

* Read config from `show run` if `show ip static route` fails

* Restore flags to ios.get_config &  use get_config where appropriate

lib/ansible/plugins/cliconf/ios.py

@@ -61,8 +61,7 @@ class Cliconf(CliconfBase):
         else:
             cmd = 'show startup-config'
 
-        flags = [] if flags is None else flags
-        cmd += ' '.join(flags)
+        cmd += ' '.join(to_list(flags))
         cmd = cmd.strip()
 
         return self.send_command(cmd)