CellServDB maintains a mapping of cell names to IP addresses of servers
serving them.

Under normal operation, CellServDB.dist (which is distributed by the
OpenAFS package) and CellServDB.local (which is normally empty, but can
be used to add local AFS cells.)

However, we patch OpenAFS's systemd unit file to instead concatenate
CellServDB.local (which is Athena Ops provided database) and
CellServDB.mousetrap (which is a bogus entry for better-mousetrapfs,
which catches and kills 'find /afs').

CellServDB.mousetrap must be concatenated at the end, as readdir on
/afs returns cells in reverse order they are in CellServDB.