test26: exit 1 on failure

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
cgmanager: remount /sys/fs/cgroup rw if needed

We should probably undo this when done, but for now let's just
make sure it fixes the issue running under systemd.

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>