Fix cpu gauge to show percent of machine cpu capacity being used by the
container. For a container using one full core out on a 4-core machine,
the gauge will show up as 25%.

Docker-DCO-1.1-Signed-off-by: Rohit Jnagal <jnagal@google.com> (github: rjnagal)
Merge pull request #136 from rjnagal/cpumask

Fix cpu gauge to show percent of machine cpu capacity being used by a container.