VLV extra tests found on bugzilla

An attachment on https://bugzilla.samba.org/show_bug.cgi?id=13951 (CVE-2019-12436) has tests and a hardening patch for after the security release.

It turns out the hardening patch was a partial fix for certain cases of CVE-2020-10730, and it is no longer applicable.

Checklist

• Commits have Signed-off-by: with name/author being identical to the commit author
• (optional) This MR is just one part towards a larger feature.
• (optional, if backport required) Bugzilla bug filed and BUG: tag added
• Test suite updated with functionality tests
• Test suite updated with negative tests
• Documentation updated
• CI timeout is 3h or higher (see Settings/CICD/General pipelines/ Timeout)

Reviewer's checklist:

• There is a test suite reasonably covering new functionality or modifications
• Function naming, parameters, return values, types, etc., are consistent and according to README.Coding.md
• This feature/change has adequate documentation added
• No obvious mistakes in the code