Assign local variable in api.v2.image_data

If local variable 'image' will be not initialized we get UnboundLocalError
while handle following exceptions:
exception.StorageFull
exception.StorageQuotaFull
exception.ImageSizeLimitExceeded
exception.StorageWriteDenied
webob.exc.HTTPError
ValueError

This is because not initialized variable 'image' used as argument of
method _restore. That is why we should initialize it.

Closes-Bug: #1310952

Change-Id: I3bf73ca272aad479416067495006476934a01dd9

glance/api/v2/image_data.py

@@ -61,6 +61,7 @@ class ImageDataController(object):
     @utils.mutating
     def upload(self, req, image_id, data, size):
         image_repo = self.gateway.get_repo(req.context)
+        image = None
         try:
             image = image_repo.get(image_id)
             image.status = 'saving'