This adds scripts using Selenium Webdriver to verify
the dashboards for Gafana, Nagios, and Prometheus are
reachable and functioning as expected. The scripts
create screenshots of each dashboard as well as
pages that can be navigated to.
It also adds the scripts to the gates for the single
and multinode deployments.
Change-Id: I1699e0ba8ff82ce8f59342cc71aad10cff7d2516
c3bef9e88f