Merge branch 'sg/stress-test'

Merge branch 'sg/stress-test'

Flaky tests can now be repeatedly run under load with the
"--stress" option.

* sg/stress-test:
  test-lib: add the '--stress' option to run a test repeatedly under load
  test-lib-functions: introduce the 'test_set_port' helper function
  test-lib: set $TRASH_DIRECTORY earlier
  test-lib: consolidate naming of test-results paths
  test-lib: parse command line options earlier
  test-lib: parse options in a for loop to keep $@ intact
  test-lib: extract Bash version check for '-x' tracing
  test-lib: translate SIGTERM and SIGHUP to an exit