add in elastic-recheck-unclassified report

this adds the new elastic-recheck-unclassified report, which
generates an html page of all the unclassified gate failures.

it also runs this command, and the elastic-recheck-graph command
not only on cron, but also on updates to the repository. In order
to do this safely, we create a new er_safe_run.sh in /usr/local
that provides a flock front end to ensure we won't race on our
html writes.

Change-Id: I624f2629e2ac19a1394866f73f1aa9ba18e968ce
Merge "add in elastic-recheck-unclassified report"