rgw: multisite refact

rgw: multisite refact

Add the possibility to deploy rgw multisite configuration with a mix of
secondary and primary zones on a same rgw node.
Before that, on a same node, all instances were either primary
zones *OR* secondary.

Now you can define a rgw instance like following:

```
rgw_instances:
  - instance_name: 'rgw0'
    rgw_zonemaster: false
    rgw_zonesecondary: true
    rgw_zonegroupmaster: false
    rgw_realm: 'france'
    rgw_zonegroup: 'zonegroup-france'
    rgw_zone: paris-00
    radosgw_address: "{{ _radosgw_address }}"
    radosgw_frontend_port: 8080
    rgw_zone_user: jacques.chirac
    rgw_zone_user_display_name: "Jacques Chirac"
    system_access_key: P9Eb6S8XNyo4dtZZUUMy
    system_secret_key: qqHCUtfdNnpHq3PZRHW5un9l0bEBM812Uhow0XfB
    endpoint: http://192.168.101.12:8080
```

Basically it's now possible to define `rgw_zonemaster`,
`rgw_zonesecondary` and `rgw_zonegroupmaster` at the intsance
level instead of the whole node level.

Also, this commit adds an option `deploy_secondary_zones` (default True)
which can be set to `False` in order to explicitly ask the playbook to
not deploy secondary zones in case where the corresponding endpoint are
not deployed yet.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1915478
Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>