cephfs: update TestCreateMountWithId to check custom id is used
cephfs: update TestCreateMountWithId to check custom id is used

Now that we have mds command function, we can use it to check for the id
we passed to CreateMountWithId appears in the session list.

Signed-off-by: John Mulligan <eda8ad33169deab44f9fe65847f99e368da6c91b@redhat.com>

ceph/go-ceph,ceph/go-ceph,ceph/go-ceph