Merge pull request #10665 from cchurch/doc_updates_for_winrm_fixes

Update windows documentation to indicate how to specify kerberos auth.

docsite/rst/intro_windows.rst

@@ -57,7 +57,7 @@ In group_vars/windows.yml, define the following inventory variables::
 
 Notice that the ssh_port is not actually for SSH, but this is a holdover variable name from how Ansible is mostly an SSH-oriented system.  Again, Windows management will not happen over SSH.
 
-If you have installed the ``kerberos`` module, Ansible will first attempt Kerberos authentication. *This uses the principal you are authenticated to Kerberos with on the control machine and not the ``ansible_ssh_user`` specified above*. If that fails, either because you are not signed into Kerberos on the control machine or because the corresponding domain account on the remote host is not available, then Ansible will fall back to "plain" username/password authentication.
+If you have installed the ``kerberos`` module and ``ansible_ssh_user`` contains ``@`` (e.g. ``username@realm``), Ansible will first attempt Kerberos authentication. *This method uses the principal you are authenticated to Kerberos with on the control machine and not ``ansible_ssh_user``*. If that fails, either because you are not signed into Kerberos on the control machine or because the corresponding domain account on the remote host is not available, then Ansible will fall back to "plain" username/password authentication.
 
 When using your playbook, don't forget to specify --ask-vault-pass to provide the password to unlock the file.