[NSHSFC-25] Maximum latency is too big

[vvalderrv]

When acting as SFF, Proxy and Classifier, NSH_SFC shows the maximum latency about 700,000 us, which is far more than the maximum latency of VPP within VxLAN encap/decap.
We need to figure out why NSH_SFC introduces that big latency to the packet processing procedure.