Upstream: don't consider default_port when matching upstreams.

Upstream: don't consider default_port when matching upstreams.

The only thing that default_port comparison did in the current
code is prevented implicit upstreams to the same address/port
from being aliased for http and https, e.g.:

	proxy_pass http://10.0.0.1:12345;
	proxy_pass https://10.0.0.1:12345;

This is inconsistent because it doesn't work for a similar case
with uswgi_pass:

	uwsgi_pass uwsgi://10.0.0.1:12345;
	uwsgi_pass suwsgi://10.0.0.1:12345;

or with an explicit upstream:

	upstream u {
	    server 10.0.0.1:12345;
	}

	proxy_pass http://u;
	proxy_pass https://u;

Before c9059bd5445b, default_port comparison was needed to
differentiate implicit upstreams in

	proxy_pass http://example.com;

and

	proxy_pass https://example.com;

as u->port was not set.