tests: Fixes zfs snapshot restore bug in tests
tests: Fixes zfs snapshot restore bug in tests

LXD was returning snapshots not in oldest-first order in some cases, and the tests were written to expect that bug.

Signed-off-by: Thomas Parrott <6b778ce645fb0e3dde76d79eccad490955b1ae74@canonical.com>

lxc/lxd,Skarlso/lxd,atxwebs/lxd,lxc/lxd,stgraber/lxd,Skarlso/lxd,lxc/lxd,stgraber/lxd,hallyn/lxd,hallyn/lxd,stgraber/lxd,lxc/lxd,hallyn/lxd,hallyn/lxd,hallyn/lxd,mjeanson/lxd,stgraber/lxd,lxc/lxd,mjeanson/lxd,lxc/lxd,Skarlso/lxd,lxc/lxd,stgraber/lxd,stgraber/lxd,mjeanson/lxd,Skarlso/lxd,hallyn/lxd,stgraber/lxd,atxwebs/lxd,atxwebs/lxd,atxwebs/lxd