mon: add `ceph fs [new|rm|ls]`

Signed-off-by: John Spray <john.spray@inktank.com>
vstart: update for newfs/rmfs changes

Signed-off-by: John Spray <john.spray@inktank.com>
test/qa: update for MDSMonitor changes

Accomodate changes:
 * data and metadata pools no longer exist by default
 * filesystem-using tests must use `fs new` to create
   the filesystem first.

Signed-off-by: John Spray <john.spray@inktank.com>
mds: journal-related debug messages

Signed-off-by: John Spray <john.spray@redhat.com>