Fixes post _strat_lock removal

Some standard request handlers need to ensure that they always do their work in
the ioloop since there is no more lock protection. This also showed up the lack
of futures support in the @return_reply decorator. There still seems to be a bit
of a reliability issue w.r.t. testutils.handle_mock_req(), but that will be
addressed later.
Yield to the ioloop at the end of each message to ensure fairness between clients
Merge pull request #24 from ska-sa/fix-stratlock-build

Fixes post _strat_lock removal