Added manila.conf details to kolla-ansible documentation

This small update is to show users where to put their manila
configuration file for kolla-ansible.

Change-Id: I050bb6e388c8b82de05e4deeaa357b98525c004e
Story: 2004414
Task: 28058

doc/source/configuration/kolla-ansible.rst

@@ -162,6 +162,7 @@ which files are supported.
    ``keystone/*``                  Extended keystone configuration.
    ``magnum.conf``                 Magnum configuration.
    ``magnum/*``                    Extended magnum configuration.
+   ``manila.conf``                 Manila configuration.
    ``manila/*``                    Extended manila configuration.
    ``murano.conf``                 Murano configuration.
    ``murano/*``                    Extended murano configuration.