Change needed in order to support --limit on mon nodes.
Otherwise, a call to `hostvars[groups[mon_group_name][0]]['_current_monitor_address']`
throws an error:
```
"The error was: 'ansible.vars.hostvars.HostVarsVars object' has no attribute '_current_monitor_address'"
```
Closes: https://bugzilla.redhat.com/show_bug.cgi?id=2014304#c28
Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>
It can be useful in a large cluster deployment to split the upgrade and
only upgrade a group of nodes at a time.
Closes: https://bugzilla.redhat.com/show_bug.cgi?id=2014304
Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>