move data away from virtual pv's

Originally created by @groente on #16211 (Redmine)

Currently a number of systems have the following storage configuration:

- lizard has a logical volume DISKNAME and feeds it to a virtual machine.

- the virtual machine sees DISKNAME as /dev/vdb and treats this as an LVM PV

- the virtual machine uses this PV for a volume group
- on this volume group is a logical volume, which is mounted in the virtual machine.

This does not play very nice with our backup system and adds several layers of complexity with close to zero benefits.

My plan is to get to the following situation:

- lizard has a logical volume DISKNAME and offers it to the vm

- the vm sees DISKNAME as /dev/vdb
- /dev/vdb has ext4 on it and is mounted in the vm.

This desired situation is already what we do on www.
This situation allows for a backup procedure that simply takes a snapshot of the logical volume on lizard, mounts it, and sends the data to the backup server.

Affected vm’s are: apt-proxy, bitcoin, isobuilder1-4, puppet-git, rsync

Parent Task: #15071 (closed)