[2.2.0] Add Git release tag as a label & enable SSL cert verification for wget

[ThilinaManamgoda]

Purpose

This PR introduces the Docker source Git release tag as a label and enable SSL verification for wget. This fixes #360, #357, #356

Goals

Introduce the Docker source Git release tag as a label.
Enable SSL verification for wget.

Approach

Use the dockerfile instruction LABEL to add Git release tag as a label.
Removes existing option --no-check-certificate for wget and update the CA certificates for Ubuntu 16.04 by installing ca-certificates package.

Test environment

Client: Docker Engine - Community
Version: 19.03.12
API version: 1.40
Go version: go1.13.10
Git commit: 48a66213fe
Built: Mon Jun 22 15:45:36 2020
OS/Arch: linux/amd64
Experimental: false

Server: Docker Engine - Community
Engine:
Version: 19.03.12
API version: 1.40 (minimum version 1.12)
Go version: go1.13.10
Git commit: 48a66213fe
Built: Mon Jun 22 15:44:07 2020
OS/Arch: linux/amd64
Experimental: false
containerd:
Version: 1.2.13
GitCommit: 7ad184331fa3e55e52b890ea95e65ba581ae3429
runc:
Version: 1.0.0-rc10
GitCommit: dc9208a3303feef5b3839f4323d9beb36df0a9dd
docker-init:
Version: 0.18.0
GitCommit: fec3683