Make collation explicit in certain tests

Platforms differ in default collation. This can result in discrepancies
in results.
Increase launcher portability

Turns out the function syntax I used is bash-specific, so use that.
Additionally, GNU sed is a bit pickier about arguments, so those need
addressing.
Clean up shell script, handle non-existent conf.

The sed replacement fails if pg_worker_list.conf doesn't exist at all,
so create a blank version of it if none exists.

Also, we should have been using -f, not -e to test for the file.