Update the drop-down options boxes in the Cluster Configuration

[aleksei-burlakov]

Here I add two changes + the test for them. Changes are

1. sle15.4+ versions uses the keyword "select" instead of "enum" for enumeratable options.
2. pacemaker 2.8+ lists possible values in the "content" section instead of the "longdesc".

[aleksei-burlakov]

I've amended the second commit (the testing commit). The first one (the payload) is from the beginning correct.

[aleksei-burlakov]

LGTM!