manila now [1] supports configuring an octal value for the
rwx permissions mode of the cephfs volumes and snapshots
and groups of these that back manila shares, snapshots,
and groups.
Expose this parameter in the backend manifests for manila
with cephfs.
[1] https://review.openstack.org/#/c/614332
Depends-On: https://review.openstack.org/#/c/638770/
Change-Id: Id8cbdfeff8299ff08a84c1c5902fb909353d4678