Ninja: fix test for js return type under rhino engine
Temporary fix for CASSANDRA-8326

This is a temporary python driver fix for CASSANDRA-8326.  The patch
has not been properly reviewed and tested by the python driver team.
The driver version bundled here can be found at the following branch:

https://github.com/thobbs/python-driver/tree/CASSANDRA-8326-temp-fix