Fix again whitespaces with python 2.7.0-2.7.3

We had a patch to fix XML whitespaces with python early than 2.7.3 at (
https://review.openstack.org/#/c/71266/ ). The function was later
changed to < 2.7.0 with:
https://review.openstack.org/#/c/93198/1/jenkins_jobs/builder.py

That apparently restore the issue with python < 2.7.3. Bump the version
check to its previous value.

Change-Id: Ib6c2bdb9f8b82c1770c44a74dfd278bf8b3ea466
Merge "Fix again whitespaces with python 2.7.0-2.7.3"