Add microversion to support extra_specs in flavor API.

Exposes flavor extra_specs in the flavor representation since
microversion 2.61. Now users can see the flavor extra-specs
in flavor APIs response only and do not need to call
``GET /flavors/{flavor_id}/extra_specs`` API.

Flavor extra_specs will be included in Response body of the
following APIs:

* ``GET /flavors/detail``
* ``GET /flavors/{flavor_id}``
* ``POST /flavors``
* ``PUT /flavors/{flavor_id}``

Part of blueprint add-extra-specs-to-flavor-list

Change-Id: I048747633babf690a63c6de9773bff5547872053

api-ref/source/flavors.inc

@@ -105,11 +105,12 @@ Response
    - swap: flavor_swap
    - rxtx_factor: flavor_rxtx_factor
    - os-flavor-access:is_public: flavor_is_public
+   - extra_specs: extra_specs_2_61
 
 
-**Example Create Flavor (v2.55)**
+**Example Create Flavor (v2.61)**
 
-.. literalinclude:: ../../doc/api_samples/flavor-manage/v2.55/flavor-create-post-resp.json
+.. literalinclude:: ../../doc/api_samples/flavor-manage/v2.61/flavor-create-post-resp.json
    :language: javascript
 
 List Flavors With Details
@@ -155,10 +156,11 @@ Response
    - swap: flavor_swap
    - rxtx_factor: flavor_rxtx_factor
    - os-flavor-access:is_public: flavor_is_public
+   - extra_specs: extra_specs_2_61
 
-**Example List Flavors With Details (v2.55)**
+**Example List Flavors With Details (v2.61)**
 
-.. literalinclude:: ../../doc/api_samples/flavors/v2.55/flavors-detail-resp.json
+.. literalinclude:: ../../doc/api_samples/flavors/v2.61/flavors-detail-resp.json
    :language: javascript
 
 Show Flavor Details
@@ -197,10 +199,11 @@ Response
    - swap: flavor_swap
    - rxtx_factor: flavor_rxtx_factor
    - os-flavor-access:is_public: flavor_is_public
+   - extra_specs: extra_specs_2_61
 
-**Example Show Flavor Details (v2.55)**
+**Example Show Flavor Details (v2.61)**
 
-.. literalinclude:: ../../doc/api_samples/flavors/v2.55/flavor-get-resp.json
+.. literalinclude:: ../../doc/api_samples/flavors/v2.61/flavor-get-resp.json
    :language: javascript
 
 Update Flavor Description
@@ -252,11 +255,12 @@ Response
    - swap: flavor_swap
    - rxtx_factor: flavor_rxtx_factor
    - os-flavor-access:is_public: flavor_is_public
+   - extra_specs: extra_specs_2_61
 
 
-**Example Update Flavor Description (v2.55)**
+**Example Update Flavor Description (v2.61)**
 
-.. literalinclude:: ../../doc/api_samples/flavor-manage/v2.55/flavor-update-resp.json
+.. literalinclude:: ../../doc/api_samples/flavor-manage/v2.61/flavor-update-resp.json
    :language: javascript
 
 Delete Flavor