utils: Remove troublesome utility methods

These are not compatible with SQLAlchemy 2.0 due to their reliance on
nested transactions. We should deprecate them first but doing so would
push the boat out further wrt how long we have to wait before achieving
compatibility with this new version.

Change-Id: If3db4e8c1b681c0c62d3f04a57f92802639b3b9b
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>