For offline machines, use the time between last backup and last change of conn dot status to decide on backup status

This seems to be used for machines with postgres. It was also updated
to put exclude and log files in the new locations.

debian-zfs doesn't exist in Ubuntu.

Split logs for tasks with same target machine but different target filesystems into
different logfiles for easier debugging.

prepare-nondebian script creates a fake excludes file for the machine now if
one doesn't exist, because I keep forgetting to do it myself for Redhat
machines and then the zfs-rsync script fails.

Add missing log directory /var/log/chem-zfs-backups
Add missing dep on rsync
Add fakeroot to Makefile to allow non-root building

Forcing arcfour causes us not to be able to back up jessie machines.