Update .gitignore
Update .gitignore

This patch[1] already explains why updating .gitignore

[1]https://review.openstack.org/#/c/466356/

Change-Id: I5ea9ddfb2a3e5827c83c6d0f164ab0aa4754ab15
Depends-On: Ifeaaa14c63158d0318218ca62ee41e98fc4c0b57
Co-Authored-By: Alex Schultz <6963656cd5f1036a86f38d6c01e67c3f63074c58@redhat.com>

openstack/puppet-gnocchi,openstack/puppet-gnocchi