ipfix probe_ptree: support configs without software RSS classes
ipfix probe_ptree: support configs without software RSS classes

eugeneia/snabb,snabbco/snabb,snabbco/snabb,snabbco/snabb,snabbco/snabb,eugeneia/snabb,snabbco/snabb,eugeneia/snabb,snabbco/snabb,eugeneia/snabb,snabbco/snabb,eugeneia/snabb,eugeneia/snabb,snabbco/snabb,eugeneia/snabb,eugeneia/snabb