test_backend: 1.9 compatibility fixes
test_backend: 1.9 compatibility fixes

Not sure how hosts was ever allowed to be a String, but sort_by
does not work on Strings in 1.9 so this was a bug before, too.
Also I'm not sure how the accept_nr variable gets shared between
threads; better just to use sockets for here...

drasch/mogilefs-client,godfat/not-used-mogilefs-client,songkick/mogilefs-client