List multiple fields tests for networks/ports

* use dictionary as input parameter in urlencode as it is a
  little simpler than two-element tuples
* add list multiple fields tests for network/port
  original tests only test one field, this patch adds another one

Change-Id: I0d8b7412dc576e5f0bb5147678721d26a24f8273
Merge "List multiple fields tests for networks/ports"