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

Fix cpu gauge to show percent of machine cpu capacity being used by a container.
For a container using one full core on a 4-core machine, the gauge will show 25% usage.

Docker-DCO-1.1-Signed-off-by: Rohit Jnagal <jnagal@google.com> (github: rjnagal)