interface: reduce duplicate code in the interface-output node
interface: reduce duplicate code in the interface-output node

Type: improvement
Change-Id: I46459a0c0a79677092aa9f8c92b67c0d06f7242e
Signed-off-by: Damjan Marion <9141bba8b2efed526e55cf796d48631af330ad98@cisco.com>

chrisy/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,FDio/vpp