vtls: remove 'detach/attach' functions from TLS handler struct

[bagder]

Unused since 7c8bae0

[icing]

So far, connection filters never had a NULL implementation of a function. Because almost all call "down". cntrl does not do that, so NULL will work (with the added check), but I am not sure if this is a good idea.

[bagder]

I was not really sure it was a good idea or not. I'll make it a dummy function instead to stick to the pattern.

[icing]

I was not really sure it was a good idea or not. I'll make it a dummy function instead to stick to the pattern.

Life Curl_cf_def_cntrl? 😌

[testclutch]

Analysis of PR #15776 at 68e0cfb3:

Test http/test_14_auth.py::TestAuth::test_14_03_digest_put_auth[0-h3] failed, which has NOT been flaky recently, so there could be a real issue in this PR.

Generated by Testclutch