This test was added in [moby@b2551c6] as part of a larger PR that implemented
unit tests in various packages. In this specific test, it looks like the
`imageSaveFunc` that's defined in the test-table was forgotten to be wired
up, causing all tests to effectively be skipped.
This patch wires up the function so that it's used in the test.
[moby@b2551c6]: b2551c619d
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>