Explicitly install `ceph-mds` package
Explicitly install `ceph-mds` package

When Manila is to be configured with CephFS backend, explicitly
install `ceph-mds` package. The newer versions of Ceph packages,
do not have the dependency between `ceph` and `ceph-mds` packages.

Change-Id: Idfd4cf7fc017ad6ced2d325356ff97cc68889dc0
Closes-Bug: #1533314

openstack/devstack-plugin-ceph,ajarr/devstack-plugin-ceph