Whitelist external mysql-connector-python req

Pip 1.5 changes how it deals with external packages:

http://www.python.org/dev/peps/pep-0438/

This is affecting OpenStack projects all over:

https://bugs.launchpad.net/openstack-ci/+bug/1266513

Applying this temporary fix for the mysql-connector-python
package.

Change-Id: I6f5a9f97a42336dc94c66b09ba81dd68bdab7803