ui,openflow: quick fix of portnames
ui,openflow: quick fix of portnames

The rule filtering functionality relies on a pre-filtering of the
graph. It broke the display of port names in OpenFlow tables.

closes #1497

skydive-project/skydive,lebauce/skydive,skydive-project/skydive,lebauce/skydive,lebauce/skydive,lebauce/skydive,skydive-project/skydive,lebauce/skydive,lebauce/skydive,lebauce/skydive,skydive-project/skydive,skydive-project/skydive,skydive-project/skydive,lebauce/skydive,skydive-project/skydive