For consistency with internal Grok specifications, run_tests.py to support
optional second argument to -r option, specifying a "runid" when generating
test results.  If not specified, the value will default to a timestamp in the
format of YYYYMMDDhhmmss.

run_tests.sh updated to include `|| exit`.
Minor cleanup following feedback from pull request
Merge pull request #151 from oxtopus/run_tests-results

Optional runid (with default) in run_tests.py