workunits: make file_layout.sh more robust
workunits: make file_layout.sh more robust

We don't have a great way to guarantee mdsmap updates, but they
should happen on their own and we can loop. Closes #1518.

Signed-off-by: Greg Farnum <0bcb4295d38ee745130ea5f2bb88ef4eef474e61@dreamhost.com>

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph