Add vendor neutral parameter fail_on_missing_module (ansible#26482)

By default, the vendor neutral modules will just go on if no
implementation module is found.
If user specifies the task argument fail_on_missing_module and
sets it to True, then we bail out the play early and report that
to the user.

lib/ansible/plugins/action/net_base.py

@@ -67,12 +67,19 @@ def run(self, tmp=None, task_vars=None):
         socket_path = self._start_connection(play_context)
         task_vars['ansible_socket'] = socket_path
 
+        if 'fail_on_missing_module' not in self._task.args:
+            self._task.args['fail_on_missing_module'] = False
+
         result = super(ActionModule, self).run(tmp, task_vars)
 
         module = self._get_implementation_module(play_context.network_os, self._task.action)
 
         if not module:
-            result['failed'] = True
+            if self._task.args['fail_on_missing_module']:
+                result['failed'] = True
+            else:
+                result['failed'] = False
+
             result['msg'] = ('Could not find implementation module %s for %s' %
                              (self._task.action, play_context.network_os))
         else:
@@ -83,6 +90,8 @@ def run(self, tmp=None, task_vars=None):
             if 'network_os' in new_module_args:
                 del new_module_args['network_os']
 
+            del new_module_args['fail_on_missing_module']
+
             display.vvvv('Running implementation module %s' % module)
             result.update(self._execute_module(module_name=module,
                           module_args=new_module_args, task_vars=task_vars,