Fix payg cert import

[mcalmer]

What does this PR change?

The payg import script look for the RMT CA certificate in the following order:

1. /usr/share/pki/trust/anchors/
2. /etc/pki/trust/anchors/

This order seems to be wrong as updates to certificates are applied to /etc/ only.
This cause old certificates are still available in /usr/... and gets imported (first match win)
while the new certificates in /etc/ are ignored.

GUI diff

No difference.

• DONE

Documentation

• No documentation needed: only internal and user invisible changes

• DONE

Test coverage

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• No tests: already covered

• Unit tests were added

• Cucumber tests were added

• DONE

Links

Port of https://github.com/SUSE/spacewalk/pull/22695

• DONE

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