[CRIU] various fixes for cgroup c/r

[Tycho Andersen]

Hi guys,

While looking into an issue which Andrey reported (which I've yet to reproduce,
but the first patch in this series will hopefully help with debugging), I
noticed that we weren't actually failing when we failed to write cgroup
properties. So, I made this fail, and it uncovered some other bugs.

The fix for memory.oom_control requires a little special casing, and I'm not
sure where is best to put this (unfortunately, the kernel does not let us write
back the same value we read). So far this is the only cgroup property like this
(well, other than devices, but we write the same value to a different file
there), so I just hooked cgroup dump for this. Let me know if there is a nicer
way.

Also, there are some other typos fixed here :)

Tycho