mds: move mds fs pools creation

mds: move mds fs pools creation

When collocating mds on monitor node, the cephpfs will fail
because `docker_exec_cmd` is reset to `ceph-mds-monXX` which is
incorrect because we need to delegate the task on `ceph-mon-monXX`.
In addition, it wouldn't have worked since `ceph-mds-monXX` container
isn't started yet.

Moving the task earlier in the `ceph-mds` role will fix this issue.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1578086
Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>