Migrate CephFs Mirroring status fetch to ceph CLI

At the time of creating this issue upstream does not expose any ceph cli to fetch the status of cephfs resource mirroring. This has to be done using locally (on the host running cephfs-mirror daemon) available admin sock communication. This is how microceph fetches the status of the snaps synchronized to remote cluster.

Eventually once this is available via a Ceph command, microceph implementation should adapt to it as well.