Fix proactive refresh

[ameba23]

There is some discussion about whether we want to keep proactive refresh or only do reshares - and we decided to leave the refresh code in for now.

The test for proactive refresh has not been updated for the new way of registering users - it is still assuming a per-user registration. In #1061 this test broke as i removed the pre-generated keyshares for dave, and i have marked the test with #[ignore].

I propose to try to fix things to try to make a refresh test which works only for the network keyshare. If it turns out to be more than a few hours work i would discuss with others as to whether to pursue it or remove the feature.