Append _wixcert_ to CA test for rollback check

[bevanweiss]

Taken from wixtoolset/wix3/pull/546, but have left out the explicit length calculation from the pwzUniquePrefix string, and using this in the compare.

Fixes wixtoolset/issues#3976

[bevanweiss]

I think maybe the whole _wixcert_x portion should disappear (and so this PR isn't so valid).
I believe the thumbprint of the certificate should be sufficient.
Any objections to changing to Thumbprints to know what activities we should / have already done (for the install / rollback)?

[robmen]

It's been a long time since I looked at the cert custom actions, but IIRC the thumbprint could be provided as a property so it wasn't necessarily a stable identifier that could be used to uninstall the certificate later. This is fuzzy, but it may be that the cert install behavior needs more of a re-design to address the suffix... which is why that issue was just hanging out unfixed.

[bevanweiss]

I suspect that most of the parameters involved in the adding certificate into the store would be properties. FriendlyName seems likely, as does Thumbprint (both so that previously unknown certificates, like self-signed) can be added.
In which case I think it would need to store some additional information to record what was installed (unsure if this can be metadata stored into the certificate store..).
I haven't had much need for WiX stuff in my work lately unfortunately, so unlikely to get much time to dig into it.
I'll close this PR.