Update .gitignore
Update .gitignore

The initial .gitignore prepared by cookiecuter has too many entries
and some entries should not be included for neutron related projects.

Change-Id: I56a838f27f780e8824b2a2e80702b60d4f16148b

stackforge/networking-nec,stackforge/networking-nec,openstack/networking-nec,openstack/networking-nec