Check for old bash versions that don't support associative arrays.
Merge pull request #408 from hjoliver/test-battery-bash-check

Check for old bash versions that don't support associative arrays.
Merge branch 'master' into 204.suite-env-file
Merge branch '204.suite-env-file' of github.com:matthewrmshin/cylc into 204.suite-env-file