Updated armband

Updated armband
Project: vswitchperf  4bd09fc0c95f89f3041e6a5a66613eb7cd7eaff8

Spirent Support for Continuous Traffic

Adding changes for supporting continuous traffic for Spirent Testcenter
The changes are as follows:
1. From send_cont_traffic invoke function in testcenter-rfc2544-rest.py
2. In testcenter-rfc2544-rest.py check for the traffic_custom
3. If the traffic_custom is 'cont' do additional configuration on
traffic.

JIRA: VSPERF-146
Change-Id: Ic963f9f0c2bd013f6e676c9d18b151ae67ff77af

Signed-off-by:    Sridhar Rao <sridhar.rao@spirent.com>