Add MKS protocol for remote consoles

MKS is the native protocol for VMware consoles and this patch is adding
API support for it. For now there is only one console type for this
protocol and this is 'webmks'. A new microversion is introduced which
adds protocol 'mks' and type 'webmks' for requesting a remote console.

Example request:

POST /servers/<uuid>/remote-consoles
{
  "remote_console": {
    "protocol": "mks",
    "type": "webmks"
  }
}

Example response:

{
  "remote_console": {
    "protocol": "mks",
    "type": "webmks",
    "url": "http://example.com:6090/mks.html?token=XYZ"
  }
}

APIImpact
Implements: blueprint vmware-webmks-console

Change-Id: I7217b999fb8d64a5646d8f20d7426c26553871d7

nova/api/openstack/api_version_request.py

@@ -46,6 +46,7 @@ REST_API_VERSION_HISTORY = """REST API Version History:
     * 2.5 - Allow server search option ip6 for non-admin
     * 2.6 - Consolidate the APIs for getting remote consoles
     * 2.7 - Check flavor type before add tenant access.
+    * 2.8 - Add new protocol for VM console (mks)
 """
 
 # The minimum and maximum versions of the API supported
@@ -54,7 +55,7 @@ REST_API_VERSION_HISTORY = """REST API Version History:
 # Note(cyeoh): This only applies for the v2.1 API once microversions
 # support is fully merged. It does not affect the V2 API.
 _MIN_API_VERSION = "2.1"
-_MAX_API_VERSION = "2.7"
+_MAX_API_VERSION = "2.8"
 DEFAULT_API_VERSION = _MIN_API_VERSION