test: Make check-storage-lvm2.testSnapshots nondestructive
test: Make check-storage-lvm2.testSnapshots nondestructive

Move to using a RAM disk, and clean up the VG after the test so that the
RAM disk device is not busy any more.

Reduce all the partition sizes so that the RAM disk doesn't consume so
much memory in our VMs, they only have 1 GiB.

cockpit-project/cockpit,cockpit-project/cockpit,garrett/cockpit,garrett/cockpit,moraleslazaro/cockpit,cockpituous/cockpit,martinpitt/cockpit,martinpitt/cockpit,mvollmer/cockpit,garrett/cockpit,deryni/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,deryni/cockpit,martinpitt/cockpit,cockpit-project/cockpit,mvollmer/cockpit,mvollmer/cockpit,deryni/cockpit,cockpituous/cockpit,deryni/cockpit,mvollmer/cockpit,martinpitt/cockpit,martinpitt/cockpit,cockpituous/cockpit,garrett/cockpit,deryni/cockpit,cockpituous/cockpit,deryni/cockpit,deryni/cockpit,cockpit-project/cockpit,garrett/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,cockpituous/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit