iptables_state: fix race condition between module and its action plugin (#1140)

* fix race condition between module and its action plugin

See https://github.com/ansible-collections/community.general/issues/1136.
Also remove irrelevant/unneeded display.v() and display.warning() around
connection reset.

* do not check for cookie if not in async mode

* add changelog fragment

plugins/modules/system/iptables_state.py

@@ -551,6 +551,18 @@ def main():
             restored_state = state_to_restore
 
     else:
+        # Let time enough to the plugin to retrieve async status of the module
+        # in case of bad option type/value and the like.
+        if _back is not None:
+            b_starter = to_bytes('%s.starter' % _back, errors='surrogate_or_strict')
+            while True:
+                if os.path.exists(b_starter):
+                    os.remove(b_starter)
+                    break
+                else:
+                    time.sleep(0.01)
+                    continue
+
         (rc, stdout, stderr) = module.run_command(MAINCOMMAND)
         if 'Another app is currently holding the xtables lock' in stderr:
             module.fail_json(