Before this patch libcontainer badly errored out with `invalid
argument` or `numerical result out of range` while trying to write
to cpuset.cpus or cpuset.mems with an invalid value provided.
This patch adds validation to --cpuset-cpus and --cpuset-mems flag along with
validation based on system's available cpus/mems before starting a container.
Signed-off-by: Antonio Murdaca <runcom@linux.com>
