Add missing validation to test_delete_saving_image

The purpose of the test_delete_saving_image test is to validate that
an image in saving state can be deleted, however the test never
actually checks that the image was actually deleted. This commit adds
an assertion to validate that.

Change-Id: Ib183db03f0d2953c61929a7f2b6bfb835a93d781
Closes-Bug: 1600340
1 file changed