Fix issues caused by foundationdb.org breakage

Fix issues caused by foundationdb.org breakage

The foundationdb.org collapse and subsequent move to GitHub created a
bit of fallout:

* Update package URLs from foundationdb.org to github.com

* Install Python package via pip as it's not published on GitHub

* Bump version to 6.3.23 as pypi has limited release selection

* Vendor the create_cluster_file.bash script (FDB elected to remove it
  from their published container builds).