On nfree, we call nfsmfs_setup will all nodes in the experiment even
though it is unlikely that any of them are in the MFS. Even so, we were
unconditionally doing a "zfs share -a" to make sure the exports table was
up to date. This hurt hard in our environment where we have a zillion users
and oodles of nodes (these are very precise thresholds!)

Also, use "mount" to get the list of mounted NFS MFS filesystems rather
than "zfs list" which likewise can be quite painful when there are a gazillion
(1 gazillion > 1 zillion) ZFS filesystems.