Set priority group only for pools with multiple members.

[velp]

This PR fixes priorityGroup set for a single member. This is related to a bug in F5 which we detected with Octavia Tempest. The fix was already tested and the number of fails decreased by 40%.

[BenjaminLudwigSAP]

What exactly does this change in the behavior of the code? At first I thought that it might work around any([]) == True, but after checking on a python3 console I found that any([]) == False, which already is the default value you're setting for enable_priority_group. So there should be no change in functionality of the code from this PR, as far as I can see.

Please also note that I deployed #153 to QA yesterday. I don't think that this made a difference for the tests, but just so you know.

[BenjaminLudwigSAP]

fixes priorityGroup set for a single member

So I assume that member.backup is not set when there is only one member? If so, please add this fact as a comment above the line you changed. Thank you.

[velp]

@BenjaminLudwigSAP I've already explained this in our meeting. This is a situation when we have at the same time:

• disabled member (aka backup) - that's why any() returns True
• single member in the pool
• priorityGroup set

[velp]

BTW: it was tested in qa-de-1 before and after your deployment and this fix worked as expected.

[BenjaminLudwigSAP]

Thank you for explaining again. PRs should always explain what exactly they're fixing.

I added my requested comment to the code.