Fix style issues in existing-neutron-network spec
Fix style issues in existing-neutron-network spec

1. Heading levels are fixed
2. Wherever lines had scope to include more words and ensuring length
is < 79

Change-Id: I5a78f88fff43b7fb1a7ce04b81172f4105b983e1

openstack/kuryr,openstack/kuryr,celebdor/kuryr,celebdor/kuryr,celebdor/kuryr-libnetwork,celebdor/kuryr-libnetwork,celebdor/kuryr-libnetwork