Revert "backup: make borg_volume prefix overridable separately from the rest"
Revert "backup: make borg_volume prefix overridable separately from the rest"

This reverts commit bb4a090a63961e48fa4af4c304c2bc46b4ab6af1.

grawity/hacks,grawity/hacks,grawity/hacks,grawity/hacks,grawity/hacks,grawity/hacks,grawity/hacks