Zypper refresh handling

[mcalmer]

clarify and unify zypper refresh handling.

Requesting refresh is a force refresh. If not forcing refresh, we let zypper decide if a refresh is needed or not.

In the meanwhile zypper has for all refresh operations a threshold to prevent useless refreshes. It would be good to trust zypper here.

@isbm : maybe you want to check this again.

[mcalmer]

@isbm : please check the new commit.

[isbm]

@mcalmer Just a nitpick: if I just checking the value, I would use get() function on the dict instead of pop(), which is modifying it. But if you want to modify it, sure.

Other then that, 👍 💚

[cachedout]

Thanks for your work here @mcalmer and for your excellent feedback, @isbm.

This looks good enough to merge for now so I'm going to go ahead and get it in. Thanks.