Add SKIP_WRITE_GIT_CHANGELOG to setup.py.
Add SKIP_WRITE_GIT_CHANGELOG to setup.py.

Sync with latest setup.py from openstack-common which adds options
to SKIP_WRITE_GIT_CHANGELOG and SKIP_GENERATE_AUTHORS.

If you set SKIP_WRITE_GIT_CHANGELOG in your environment it will speed
up sdist creation by 10-20 seconds which also helps make tox run
faster (because it runs sdist).

Change-Id: I5da708d2e9547d5e554cf49ecfcf39591de6a4e5

n0ano/gantt,n0ano/gantt