Few improvement to run GDK in the cloud

What does this Merge Request do?

This is a more opinionated MR.

Use listen address instead of hostname in some places because the hostname address might be bound to an IP that the machine in the cloud might not have direct access to. So the cloud computer will set 0.0.0.0 as listen address, while the hostname is some domain that will resolve to a public IP on the interwebs.

Closes #978 (closed)

gdk.yml

The gdk.yml I was using for this:

hostname: one.gdk.iotcl.net
listen_address: 0.0.0.0
port: 443
https:
  enabled: true

nginx:
  enabled: true
  http:
    enabled: true
    port: 80
  ssl:
    certificate: one.gdk.iotcl.net.pem
    key: one.gdk.iotcl.net-key.pem

geo:
  enabled: true
  node_name: one.gdk.iotcl.net

sshd:
  enabled: true
  listen_port: 2222

sshd & nginx

I'm running nginx and sshd without sudo. I've achieved this by running:

sudo setcap CAP_NET_BIND_SERVICE=+eip /usr/sbin/nginx
sudo setcap cap_setuid,cap_setgid,cap_net_bind_service+eip /usr/sbin/sshd

TLS

I'm using a self-signed cert generated on my local machine with mkcert and scp'd it over to the GCP VM.

Merge Request checklist

• Tests added for new functionality. If not, please raise Issue to follow-up.
• This change is backward compatible. If not, please include steps to communicate to our users.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.