This patch adds an octavia-wsgi script that gets installed with Octavia
for backward compatibility on the stable branches.
The pbr wsgi_scripts function no longer generates this script
automatically due to recent changes in setuptools.
This is a stable branch only patch.
Change-Id: I7e0b17dbf9284db27e183a9a27e716266e26a237
(cherry picked from commit b8824ede82)