Fix createServerProps in csharp/IceSSL/configuration

[bernardnormier]

I find this conversion logic unexpected - and ideally we should fix it and just "convert" with: https://github.com/zeroc-ice/ice/blob/2846e40a8ea07d870d762d89b2075071ab04aba2/csharp/src/Ice/Properties.cs#L285

This is however not the focus of this PR.

Originally posted by @bernardnormier in https://github.com/zeroc-ice/ice/pull/2812#discussion_r1780165712

[bernardnormier]

We actually have the same code in the C++ IceSSL/configuration - it's not C# specific.

[pepone]

Not clear that we should use getPropertiesForPrefix here, this method is just getting the SSL certs default dir, the default host, and the IPv6 settings. We don't want to accidentally set other SSL properties that can influence the test case.

[bernardnormier]

Ok, I am leaving this as-is.