Updated armband

Updated armband
Project: vswitchperf  77de48c31767556fb9f0de76285d1beed16dd828

Xena: Modify aggregate_stats one port no stats when bi-direction

Xena exception when no stats collected on receive on one port
during bi-directional traffic. Modify aggregate_stats in the
XenaDriver.py, add judge whether the two port both has stats,
if one port has no stats, the result use the port's value which
has stats.

JIRA: VSPERF-327

Change-Id: I18c349d609a2834907f0383dbfbebd5cd281f541
Signed-off-by: liting <tli@redhat.com>