We only clobber old backups now if we're successful in doing the
new backup. In the past if we failed half way through a new backup
we would of already removed our old backups and lost that data.

If we're excluding any data or system dirs we want to see what the
system base dirs are in the output.

Before this change, for --exclude-data to work one must specify
--exclude-system too. This is no longer the case and both options
now work independently.

We made an assumption that the filesystem has not been snapshotted,
in the case that it could be snapshotted we certainly do not want
to exclude mysql & pgsql from the backups.

Treat /tmp and /var/tmp as data directories

This will help in future when we need to do cleanups