Use go-sockaddr to parse address strings

[aaronhurt]

Use go-sockaddr to parse proxy listeners, consul service address and the proxy local ip to allow more dynamic configuration of address strings.

[aaronhurt]

This should allow more dynamic configuration of listeners and advertised addresses when running within a container environment.

Basic Example:

./fabio -proxy.addr '{{ GetInterfaceIP "en0" }}:4567' \
-ui.addr '{{ GetInterfaceIP "en0" }}:1234' \
-registry.consul.register.addr '{{ GetInterfaceIP "en0" }}:1234'

Renders:

2019/04/30 17:52:10 [INFO] Admin server listening on "10.16.0.29:1234"
2019/04/30 17:52:10 [INFO] Waiting for first routing table
2019/04/30 17:52:10 [INFO] consul: Using dynamic routes
2019/04/30 17:52:10 [INFO] consul: Using tag prefix "urlprefix-"
2019/04/30 17:52:10 [INFO] consul: Watching KV path "/fabio/config"
2019/04/30 17:52:10 [INFO] consul: Watching KV path "/fabio/noroute.html"
2019/04/30 17:52:10 [INFO] consul: Registered fabio as "fabio"
2019/04/30 17:52:10 [INFO] consul: Registered fabio with id "fabio-ahurt1.local-1234"
2019/04/30 17:52:10 [INFO] consul: Registered fabio with address "10.16.0.29"
2019/04/30 17:52:10 [INFO] consul: Registered fabio with tags ""
2019/04/30 17:52:10 [INFO] consul: Registered fabio with health check to "http://[10.16.0.29]:1234/health"
2019/04/30 17:52:10 [INFO] HTTP proxy listening on 10.16.0.29:4567

[pschultz]

Looks good to me!

[aaronhurt]

Thank you!