lxd/instance/drivers/driver/qemu: Add revert arg to qemuCreate and don't call d.Delete() in revert steps
lxd/instance/drivers/driver/qemu: Add revert arg to qemuCreate and don't call d.Delete() in revert steps

Avoids removing storage volume if revert occurs due to existing storage volume.

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

stgraber/lxd,stgraber/lxd,hallyn/lxd,stgraber/lxd,lxc/lxd,hallyn/lxd,hallyn/lxd,atxwebs/lxd,atxwebs/lxd,stgraber/lxd,hallyn/lxd,hallyn/lxd,stgraber/lxd,lxc/lxd,stgraber/lxd,atxwebs/lxd,stgraber/lxd,lxc/lxd,lxc/lxd,lxc/lxd,lxc/lxd,hallyn/lxd,lxc/lxd,atxwebs/lxd