QVM-APP-NG tests hanging and exceeding gitlab timeout

[appleby]

For example:

https://gitlab.com/rigetti/forest/qvm/-/jobs/472119379

It looks like the tests are hanging on the final test in test-safety-hash.lisp, namely QVM-APP-NG-TESTS::TEST-SAFETY-HASH-CONCURRENT-WRITE-AND-REMHASH.

Unclear if the test itself is poorly written and racy, or if there some genuine bug in the QVM-APP-NG.SAFETY-HASH implementation on SBCL.