Return host's meminfo file if no memory cgroup
Return host's meminfo file if no memory cgroup

If memory cgroup is not available (that is, we can't find a
memory cgroup for the reading task), then just return the
contents of the host's /proc/meminfo.  (Same for all proc file
reads)

Closes #30

Signed-off-by: Serge Hallyn <3df611b026e4639bee8aef7a4beb2e39fcebb313@ubuntu.com>

ralt/lxcfs,rhatdan/lxcfs,ralt/lxcfs,evgeni/pkg-lxcfs-debian,Xeno22/lxcfs,Xeno22/lxcfs,rhatdan/lxcfs,evgeni/pkg-lxcfs-debian