Fix the race condition again and correct some small typos to be in line with the incremental patches to be proposed.
* bzrlib/transport/http/_pycurl.py: (PyCurlTransport._curl_perform): Why not inverting them ?
* bzrlib/tests/test_http.py: (TestWallServer.test_http_has): Whatever we try, httplib still may raise BadStatusLine, which will be translated to InvalidHttpResponse, so catch that too.
* bzrlib/tests/HTTPTestUtil.py: (WallRequestHandler.handle_one_request): Previous fix was not enough, revert it.