Add logic to handle when all aggregators configured are inaccessible

[machawk1]

The MemGator instance at ODUCS is still downit's back up and the secondary aggregator is crashing due to memory issues. There ought to be complete fall-through logic for Mink to handle the inability to do its job more gracefully.

Ideally the logic for client-side aggregation will be merged in but until then, when no aggregators are available, there ought to be an indication in the UI as such.