Feature Request: Support Docker CE 18.03

[MarcPow]

Is this a request for help?:

No

Is this an ISSUE or FEATURE REQUEST? (choose one):

Feature Request

What version of acs-engine?:

0.23.1

"dockerEngineVersion": {
  "allowedValues": [
    "17.05.*",
    "17.04.*",
    "17.03.*",
    "1.13.*",
    "1.12.*",
    "1.11.*"
  ],
  "metadata": {
    "description": "The docker engine version to install."
  },
  "type": "string"
},

[CecileRobertMichon]

Sadly, because of unresolved license limitations we are currently unable to move to new Docker CE versions (see Azure/AKS#63 for context). There has been a push to move to Moby instead, you can track the effort at #3896

[PatrickLang]

Docker EE-basic 18.03 is available for all licensed Windows Server customers. I'm tracking this upgrade in #3852

Linux users would need their own Docker EE license.