Bypass loopback prevention for deliberate loopbacks (master)

Sometimes you may want to query a separate local graphite-web instance and if you have configured one or more of your clusters hosts with a hostname of localhost or an IP of 127.x.x.x then this would be the case so with this patch they is treated as a remote host.

Master port of https://github.com/graphite-project/graphite-web/pull/1069