Upgrade to pants 0.0.24

The biggest highlight from the changelog at
https://pypi.python.org/pypi/pantsbuild.pants/0.0.24 is this will enforce
python2.7 across the repository.

Testing Done:
[tw-172-25-132-201 aurora (yasumoto/pants_0.0.24)]$ ./build-support/jenkins/build.sh

Bugs closed: AURORA-363

Reviewed at https://reviews.apache.org/r/26378/