Backup the libvirtd.conf and qemu.conf with timestamp

[paulbicheler]

Running ./libvirt_configuration.sh backs up both files with the postfix _old. If you run the script twice then you're overwriting the original backup, overwrite the backup with the new version and delete it since the mv deleted it from the git working copy.

A cp would be better and the backup should have a timestamp appended to it to make sure its not erased.
Maybe something like this
mv /etc/libvirt/libvirtd.conf /etc/libvirt/libvirtd.conf.$(date+"%s").old
and
mv "mv /etc/libvirt/qemu.conf /etc/libvirt/qemu.conf.$(date+"%s").old"