Avoid redeploying an unchanged topology

Currently, if a topology is built from a provider/descriptor pair, Knox checks the content of the "new" topology upon "onFileChange" (touch descriptor) and does not generate the topology if it's the same as the currently deployed topology.

This check is not implemented on the old-style XML-based topology handling path.

Note: as a side effect, touching a topology file will no longer trigger the topology redeployment.