Minor cleanups in thing.tasks
Change thing.tasks to use a synchronized cache variable to regulate broken API backoff timers
Probably helps if I take out the 'raise Exception' testing code :|
Change tasks backend to only prefetch a single task again
Misc thing.tasks cleanups, this code needs refactoring :(
Comment out the Locations check in thing.tasks.asset_list until I can work out why it sometimes triggers 135 errors
Improve error handling of 901, 902 and 904 errors.