Disable tarball content type check in ingestion script

[bedroge]

This check caused failures for ingesting init tarballs built with the bot (which names the tarballs like eessi-2023.06-software-<date>.tar.gz, and the check would fail because of the software part in the filename) in EESSI/software-layer#524. The check is a bit useless anyway, so I've disabled it, and also disabled the tests. The code is still there in case we do want to use it again / in a slightly different way.

$ ./test-ingest-tarball.sh 
ERROR: /cvmfs/software.eessi.io/versions/2000.01 does not point to an existing directory!
Ran 23 tests, 23 succeeded, 0 failed.

(the error is actually due to another change in the ingestion script)

[bedroge]

Also made a small fix/improvement to the test script, and it no longer prints an error (which was shown because it cannot actually do the Lmod cache updates, it's now just being ignored):

$ ./test-ingest-tarball.sh 
Ran 23 tests, 23 succeeded, 0 failed.