Draft: over master: improve NETCONF performance
... by retrieving data nodes only once from the sysrepo datastore and iterating through them to get the leaves and leaf-list nodes that are required, as opposed to retrieving each and every leaf and leaf-list node from the datastore.
This empirically reduced the time required to push a configuration of 60k leaves and leaf-list nodes from approximately 9m30s to 3s.
Closes #2400 (closed).
Edited by Andrei Pavel