mgr/volumes: Move ganesha common config to vstart

mgr/volumes: Move ganesha common config to vstart

This is a preparatoy patch before calling orchestrator for nfs cluster
deployment. All the ganesha config is moved to vstart. Keyring creation is also
taken care by vstart.

The volumes fs nfs cluster create interface does the following things:
1) Create a common recovery pool for all ganesha clusters. Each cluster will
   have their own namespace.
2) Create an empty rados conf object named 'conf-nfs' for saving all export
   urls.

Call to orch interface will be done in future patch.

Signed-off-by: Varsha Rao <varao@redhat.com>