Python's httplib does not graciously handle disconnections from the http server, resulting in BadStatusLine errors.
See https://bugs.python.org/issue3566 "httplib persistent connections violate MUST in RFC2616 sec 8.1.4."
This was fixed in Python 3.5.
Work around it for now.
Taught bitcoind to close the HTTP connection after it gets a 'stop' command,
to make it easier for the regression tests to cleanly stop.
Move bitcoinrpc files to correct location.
Tidied up the python-based regression tests.