python: make python idl unicode-tolerant

python: make python idl unicode-tolerant

Ensure that JSON is utf-8 encoded and that bytes sent/received on
the stream sockets are in utf-8 form. Add a test case to verify
that unicode data can be sent/received successfully using Python
IDL module.

Co-authored-by: Terry Wilson <twilson@redhat.com>
Signed-off-by: Terry Wilson <twilson@redhat.com>
Signed-off-by: Lance Richardson <lrichard@redhat.com>
Signed-off-by: Russell Bryant <russell@ovn.org>