Topology port mapping does not honour descriptors

In certain environments, such as in recent Cloudera offerings, XML-based topologies are not in use (and are removed every time Knox is (re)-started. Instead, topologies are produced using Knox's Simplified Descriptor Files).

The problem is, that the current topology port mapping implementation ignores artifacts from the $KNOX_CONF_FOLDER/descriptors and only considers $KNOX_CONF_FOLDER/topologies. This needs to be fixed.