Add host/hostId to instance action events API

This patch adds a new microversion to
``GET /servers/{server_id}/os-instance-actions/{req_id}`` API to
include the ``host`` field for admin and an ``hostId`` for all users
by default. And the display of newly added ``host`` field will be
controlled by the same policy as the ``traceback`` field.

The newly added fields can be used to determine on which host a
given action event occurred.

Part of blueprint: add-host-to-instance-action-events

Change-Id: I2f8b4a12a088b9ed96b428eafde2e0c478fb1db5

doc/api_samples/versions/versions-get-resp.json

@@ -22,7 +22,7 @@
                 }
             ],
             "status": "CURRENT",
-            "version": "2.61",
+            "version": "2.62",
             "min_version": "2.1",
             "updated": "2013-07-23T11:33:21Z"
         }