fixup! component/nxdtest: v↑ (namespaces, /tmp-on-tmpfs, cancellation)
Preserve "disk" group to stay in /etc/group as explained in nexedi/nxdtest@6f75fa90 because slapos.core tests use this.
Preserve "disk" group to stay in /etc/group as explained in nexedi/nxdtest@6f75fa90 because slapos.core tests use this.