Fix api version mismatch return code

According to API-WG guideline, if the requested microversion is not
supported by the API, we should return 406: Not Acceptable instead of
the default 500: Server Error or 400: Bad Request.

Change-Id: I6314e633b74053e8a770388aeb21f1124ac6ab73

api-ref/source/status.yaml

@@ -42,6 +42,9 @@
 405:
   default: |
     Method is not valid for this endpoint.
+406:
+  default: |
+    The requested API version is not supported by the API.
 409:
  default: |
     This operation conflicted with another operation on this resource.

api-ref/source/versions.inc

@@ -59,6 +59,7 @@ Response Codes
 .. rest_status_code:: error status.yaml
 
    - 404
+   - 406
    - 503
 
 Response Parameters

senlin/api/middleware/fault.py

@@ -52,6 +52,7 @@ class FaultWrapper(wsgi.Middleware):
         'FeatureNotSupported': webob.exc.HTTPConflict,
         'Forbidden': webob.exc.HTTPForbidden,
         'InternalError': webob.exc.HTTPInternalServerError,
+        'InvalidGlobalAPIVersion': webob.exc.HTTPNotAcceptable,
         'InvalidParameter': webob.exc.HTTPBadRequest,
         'InvalidSchemaError': webob.exc.HTTPBadRequest,
         'MethodVersionNotFound': webob.exc.HTTPBadRequest,