TLS docker connection

[volodimyr]

#603

1. Run docker and provide server certificates.
   sudo dockerd -H=0.0.0.0:2376 --tlsverify --tlscacert=ca.pem --tlscert=server-cert.pem --tlskey=server-key.pem

2. Set DOCKER_HOST accordingly.

3. Add config.yml new tls config such as client certificates and optionally host and verify:

tls:
  enable: true
  caCertPath: "ca.pem"
  certPath: "cert.pem"
  keyPath: "key.pem"
  host: "0.0.0.0"
  insecureSkipVerify: false

4. go run main.go (with the provided config dir)