Review Ia66e44e530799ce6531922dcf6a84e38528c8725 changes OSC's server
commands to use the image client rather than compute clirnt (yay!)
but we never really tested any of this in functional tests. This review
adds a simple functional test (in the new style) to watch the client
change; it passes locally for me without the client change, due to timing
we went ahead and merged that first.
Change-Id: I5529f412578c50090e70d17aa0129217bf803fed