bitbake/xmlrpc: Modify xmlrpc server to work with Python 2.7

bitbake/xmlrpc: Modify xmlrpc server to work with Python 2.7

Python 2.7's library changes some of xmlrpclib's internal implementation such
that interacting with a proxy to BitBakes SimpleXMLRPCServer would cause
BitBake to crash.

The issue was traced to changes in the xmlrpclib.Transport implementation and
Python bug #8194 (http://bugs.python.org/issue8194).

This patch introduces a workaround by create a subclass of
xmlrpclib.Transport, which overrides the offending methods with the Python
2.6.6 implementation copy and pasted from the Python 2.6.6 xmlrpclib, and
using this BBTransport implementation for both xmlrpclib.Server objects we
create.

Signed-off-by: Joshua Lock <josh@linux.intel.com>