Allow admins to share images regardless of owner.

Updates the Glance DB's is_image_sharable function so that
an admin can share an image regardless of the context ownership.

This fixes issues when trying to write Glance functional tests
which use the noauth middleware (UnauthenticatedContextMiddleware).

The motivation behind this change is I'd like to write some
functional tests for image-members that work with noauth.

Fix bug 1021054

Change-Id: I6d939876a4c4bf5f191463f5ca434fc524a6ac59

glance/db/simple/api.py

@@ -290,14 +290,14 @@ def is_image_mutable(context, image):
 
 def is_image_sharable(context, image, **kwargs):
     """Return True if the image can be shared to others in this context."""
-    # Only allow sharing if we have an owner
-    if context.owner is None:
-        return False
-
     # Is admin == image sharable
     if context.is_admin:
         return True
 
+    # Only allow sharing if we have an owner
+    if context.owner is None:
+        return False
+
     # If we own the image, we can share it
     if context.owner == image['owner']:
         return True

glance/db/sqlalchemy/api.py

@@ -267,14 +267,14 @@ def is_image_mutable(context, image):
 
 def is_image_sharable(context, image, **kwargs):
     """Return True if the image can be shared to others in this context."""
-    # Only allow sharing if we have an owner
-    if context.owner is None:
-        return False
-
     # Is admin == image sharable
     if context.is_admin:
         return True
 
+    # Only allow sharing if we have an owner
+    if context.owner is None:
+        return False
+
     # If we own the image, we can share it
     if context.owner == image['owner']:
         return True

glance/tests/unit/test_context.py

@@ -102,12 +102,12 @@ def test_empty_private_owned(self):
 
     def test_empty_shared(self):
         """
-        Tests that an empty context (with is_admin set to True) can
+        Tests that an empty context (with is_admin set to False) can
         not share an image, with or without membership.
         """
-        self.do_sharable(False, 'pattieblack', None, is_admin=True)
+        self.do_sharable(False, 'pattieblack', None, is_admin=False)
         self.do_sharable(False, 'pattieblack', _fake_membership(True),
-                         is_admin=True)
+                         is_admin=False)
 
     def test_anon_public(self):
         """