In some environments running older versions of gunicorn in the
amphora image, gunicorn can fail to start do to /dev/log socket
issues (timing, configuration, etc.).
This patch sets up a dedicated rsyslog socket /run/rsyslog/octavia/log
for gunicorn and haproxy to use. This should resolve any issues with
systemd overriding the /dev/log socket.
This also bumps the gunicorn minimum verison to 19.9.0.
Change-Id: I1e1ad8fde2ad8c1ffba95b1867afb130503b0a5b
afa917a3de