[nova][tempest] Should we make image certificate validation a configurable feature?

Hello all,

$subject, this came up downstream after we noticed failures due to a race within the ServerShowV263Test test that I've documented in the following upstream bug:

tempest.api.compute.servers.test_servers.ServerShowV263Test only passing when image has already been cached https://bugs.launchpad.net/tempest/+bug/1831866

As the test itself is pretty useless without valid certs, signed images etc I'd like to make the overall feature optional within Tempest and wire up some additional configurables for anyone looking to actually test this correctly. I've received some feedback in the review but this has stalled so I wanted to see if I could get things moving again by posting to the ML.

Thanks in advance,