Attaching a volume returns HTTP 202

Instead of returning an HTTP 200 and a `volumeAttachment` object,
attaching a volume to an instance returns HTTP 202 starting from API
version 2.101.

To keep the functionality for older API versions, we move the
`_attach_volume()` method from n-api to n-conductor and either do a call
or a cast depending on whether the API needs to return a value.
n-conductor then handles reserving the block_device_mapping's device by
calling n-compute before it starts the previously-already-async volume
attachment.

We have to move `_check_attach_and_reserve_volume` into compute utils,
because it's getting called in both conductor and compute api (for the
shelved offloaded attach).

The new RPC method in the conductor needs a long timeout when used with
API versions less than the new 2.101, because it waits for the call to
`reserve_block_device_name()` in nova-compute which already needs a long
timeout.

Updating the functional tests' `post_server_volume()` and
`_attach_volume()` to not return the attachment anymore is possible, as
no test uses the returned values.

Change-Id: I4d38c2679f0e88cca30055a9c8c45ba1dd6fb5ef
Implements: blueprint async-volume-attachments
Signed-off-by: Johannes Kulik <johannes.kulik@sap.com>

doc/api_samples/os-volume_attachments/v2.101/attach-volume-to-server-req.json

@@ -0,0 +1,7 @@
+{
+    "volumeAttachment": {
+        "volumeId": "a07f71dc-8151-4e7d-a0cc-cd24a3f11113",
+        "tag": "foo",
+        "delete_on_termination": true
+    }
+}

doc/api_samples/os-volume_attachments/v2.101/list-volume-attachments-resp.json

@@ -0,0 +1,22 @@
+{
+    "volumeAttachments": [
+        {
+            "attachment_id": "979ce4f8-033a-409d-85e6-6b5c0f6a6302",
+            "delete_on_termination": false,
+            "device": "/dev/sdc",
+            "serverId": "7696780b-3f53-4688-ab25-019bfcbbd806",
+            "tag": null,
+            "volumeId": "227cc671-f30b-4488-96fd-7d0bf13648d8",
+            "bdm_uuid": "c088db45-92b8-49e8-81e2-a1b77a144b3b"
+        },
+        {
+            "attachment_id": "c5684109-0311-4fca-9814-350e46ab7d2a",
+            "delete_on_termination": true,
+            "device": "/dev/sdb",
+            "serverId": "7696780b-3f53-4688-ab25-019bfcbbd806",
+            "tag": "foo",
+            "volumeId": "a07f71dc-8151-4e7d-a0cc-cd24a3f11113",
+            "bdm_uuid": "1aa24536-6fb5-426c-8894-d627f39aa48b"
+        }
+    ]
+}

doc/api_samples/os-volume_attachments/v2.101/update-volume-attachment-delete-flag-req.json

@@ -0,0 +1,10 @@
+{
+    "volumeAttachment": {
+        "volumeId": "a07f71dc-8151-4e7d-a0cc-cd24a3f11113",
+        "id": "a07f71dc-8151-4e7d-a0cc-cd24a3f11113",
+        "serverId": "fddf0901-8caf-42c9-b496-133c570b171b",
+        "device": "/dev/sdb",
+        "tag": "foo",
+        "delete_on_termination": true
+    }
+}

doc/api_samples/os-volume_attachments/v2.101/volume-attachment-detail-resp.json

@@ -0,0 +1,11 @@
+{
+    "volumeAttachment": {
+        "attachment_id": "721a5c82-5ebc-4c6a-8339-3d33d8d027ed",
+        "delete_on_termination": true,
+        "device": "/dev/sdb",
+        "serverId": "7ebed2ce-85b3-40b5-84ae-8cc725c37ed2",
+        "tag": "foo",
+        "volumeId": "a07f71dc-8151-4e7d-a0cc-cd24a3f11113",
+        "bdm_uuid": "c088db45-92b8-49e8-81e2-a1b77a144b3b"
+    }
+}

doc/api_samples/versions/v21-version-get-resp.json

@@ -19,8 +19,8 @@
             }
         ],
         "status": "CURRENT",
-        "version": "2.100",
+        "version": "2.101",
         "min_version": "2.1",
         "updated": "2013-07-23T11:33:21Z"
     }
-}
+}

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

@@ -22,7 +22,7 @@
                 }
             ],
             "status": "CURRENT",
-            "version": "2.100",
+            "version": "2.101",
             "min_version": "2.1",
             "updated": "2013-07-23T11:33:21Z"
         }