[APIImpact] Correct API response code for PUT /v2/cache/{image_id}

PUT /v2/cache/{image_id} returns HTTP 200 response code to user but as per
proposal it should be HTTP 202. This change returns HTTP 202 response to
user.

Closes-Bug: #1971521
Change-Id: I6a875a38bef5beafe352ab3320f3fd199db89aa1
(cherry picked from commit ecb040c177)

api-ref/source/v2/cache-manage.inc

@@ -33,7 +33,7 @@ Queue image
 Queues image for caching.
 *(Since Image API v2.14)*
 
-Normal response codes: 200
+Normal response codes: 202
 
 Error response codes: 400, 401, 403, 404
 

glance/api/v2/cached_images.py

@@ -238,7 +238,9 @@ class CachedImageDeserializer(wsgi.JSONRequestDeserializer):
 
 
 class CachedImageSerializer(wsgi.JSONResponseSerializer):
-    pass
+
+    def queue_image_from_api(self, response, result):
+        response.status_int = 202
 
 
 def create_resource():

glance/tests/functional/v2/test_cache_api.py

@@ -79,7 +79,7 @@ class TestImageCache(functional.SynchronousAPIBase):
         if response.status_code == 200:
             return response.json
 
-    def cache_queue(self, image_id, expected_code=200):
+    def cache_queue(self, image_id, expected_code=202):
         # Queue image for prefetching
         path = '/v2/cache/%s' % image_id
         response = self.api_put(path)