This commit uses the new skip test funcationality added in
232b6665bc to skip the zmq tests if the
python zmq module is not available or if bitcoind has been built without
zmq support.
This removes the zmq-specific logic from test_runner.py. In general it's
better if test_runner.py has no knowledge of special cases for
individual tests and is a general purpose test runner.
This commit fixes the module-level docstrings for the tests and helper
modules in qa. Many of these tests were uncommented previously - this
commit ensures that every test case has at least a minimum level of
commenting.