So it turns out that without 'mode http' redirects and rewrites
will not happen, and we're relying on it for multiple things.
Switch neutron to use http-tunnel mode instead which seems to work,
we've had no errors in our setup.
See:
https://www.haproxy.org/download/1.5/doc/configuration.txt
Quoute:
" - tunnel : only the first request and response are processed,
everything else is forwarded with no analysis."
Fixes: bba80acc8b78ab3a34d61b3d0b496551e5a9258e
Change-Id: I0d9abe9731fba1e4deb64932e859f991648bb1ec
ee67917c49