Plumb through an fs-install makefile target and fixes to ops-install.

This officially drops the pretense that fs nodes can operate with minimal
Emulab software. If you have a seperate fs node, it had better be dedicated
to Emulab!

However, it still doesn't do everything. In particular, accounts are not
installed. This has never been needed for serving NFS, but is needed for
the samba stuff to work correctly.

Also, you cannot do an fs node software install from boss yet as we do not
mount fs filesystems on boss. You really cannot do a full ops install from
boss either since we don't mount ops' /usr/local/etc/emulab directory.