default snapshot_root doesn't follow FHS

[Jonathan McClare]

Binary package hint: rsnapshot

The default snapshot_root doesn't follow the filesystem hierarchy standard
(FHS).

The default root is `/var/cache/rsnapshot/`

According to the [Filesystem Hierarchy Standard](http://www.pathname.com/fhs/),
[`/var/cache/`](http://www.pathname.com/fhs/pub/fhs-2.3.html#VARLIBVARIABLESTATEINFORMATION)
is for files that can be re-generated by the application.

While the latest backup can be regenerated, older increments cannot. Further,
a backup is not like a cache that the software can still run slowly without. If
your backup is not available at some time because the system cleared it out to
temporarily save space (as you can do with cache files), or it gets wiped out
upon reboot because `/var/cache` is stored on a RAM drive, the backup software
is not doing it's job.

By default, backups should go in
[`/var/lib/rsnapshot/`](http://www.pathname.com/fhs/pub/fhs-2.3.html#VARCACHEAPPLICATIONCACHEDATA)

I found this in ubuntu 8.04 and 8.10.

ProblemType: Bug
Architecture: i386
Dependencies:

DistroRelease: Ubuntu 8.10
Package: rsnapshot None [modified: /var/lib/dpkg/info/rsnapshot.list]
PackageArchitecture: all
ProcEnviron:
 PATH=/home/username/bin:/home/username/local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
 LANG=en_CA.UTF-8
 SHELL=/bin/bash
SourcePackage: rsnapshot
Uname: Linux 2.6.27-17-generic i686