doc(XCP-ng) Fix broken links in the XCP-ng documentation

[thomas-dkmt]

In the XCP-ng documentation, some links pointed to locations that were obsolete or just don't exist anymore (404 error, and some 503 errors).

• Wherever a more appropriate target location could be found, the links are now fixed.
• One dead link has been replaced by the actual, relevant content.
• Links where no substitute could be found have been removed.

[Fohdeesha]

So for the "Follow this (ignore steps 6 and 7, do not try to install the tools yet) https://support.citrix.com/article/CTX215427" line, I found a wayback copy of it, and all it's saying to do is delete two registry folders:

HKLM\SYSTEM\CurrentControlSet\Enum\XENBUS
HKLM\SYSTEM\CurrentControlSet\Enum\XENVIF

given half of the other steps in this list in our docu is also deleting registry keys, we can just put the two keys directly in a new line there, and get rid of the instruction line with this dead link

[dinhngtu]

Hi, I've created a PR with instructions for using XenClean (#326). That should replace the old instructions for removing old Citrix drivers.

[stormi]

Is the merge from master into this branch on purpose? If it is, we usually prefer a rebase of the PR branch over a merge commit.

[stormi]

There's a conflict with the master branch. You'll need to rebase on master (and solve the conflict in the process).

[stormi]

Were the last pushes just rebases on master, or were there other fixes that we should review?

[thomas-dkmt]

Were the last pushes just rebases on master, or were there other fixes that we should review?

There are no other fixes, just rebases on master and solving the merge conflict