metrics/network: Cleanup README file
metrics/network: Cleanup README file

Fixes grammatical issues, spelling, and reflows text in
metrics/network/README.md

Signed-off-by: Brett T. Warden <3c49f16b9d4a3f688e955241c679cb8951e4845a@intel.com>

MarioCarrilloA/tests,sboeuf/tests,chavafg/tests,bwarden/tests,bwarden/tests,clearcontainers/tests,sboeuf/tests,devimc/tests,devimc/tests,clearcontainers/tests,MarioCarrilloA/tests,chavafg/tests