Currently placement records REMOTE_ADDR environment as source ip but
this environment points load balancer ips instead of actual client ips
when placmenet runs behind load balancers like haproxy.
This change enables HTTPProxyToWSGI middleware to parse request
headers to look up actual client address.
Story: 2009049
Task: 42819
Change-Id: I4d15201dd2f94d00f4f2b53f773511ea020ef4ac