Enhance error message about missing ControlPersist

ansible_ssh_args is good for playbook, but in the ~/.ansible.cfg
file, it should be ssh_args in a specific section.

lib/ansible/runner/connection_plugins/ssh.py

@@ -349,7 +349,7 @@ class Connection(object):
                 raise errors.AnsibleError('Using a SSH password instead of a key is not possible because Host Key checking is enabled and sshpass does not support this.  Please add this host\'s fingerprint to your known_hosts file to manage this host.')
 
         if p.returncode != 0 and controlpersisterror:
-            raise errors.AnsibleError('using -c ssh on certain older ssh versions may not support ControlPersist, set ANSIBLE_SSH_ARGS="" (or ansible_ssh_args in the config file) before running again')
+            raise errors.AnsibleError('using -c ssh on certain older ssh versions may not support ControlPersist, set ANSIBLE_SSH_ARGS="" (or ssh_args in [ssh_connection] section of the config file) before running again')
         if p.returncode == 255 and (in_data or self.runner.module_name == 'raw'):
             raise errors.AnsibleError('SSH Error: data could not be sent to the remote host. Make sure this host can be reached over ssh')