Fix build cycle between xenstore and xenstore_transport by removing
the client_unix test.

This whole test should be moved to a different repository, leaving
this one as the `portable core`.

Signed-off-by: Anil Madhavapeddy <anil@recoil.org>
Merge pull request #9 from avsm/fix-build-cycle

Fix build cycle between xenstore and xenstore_transport by removing