Added traffic update capability to Ixload TG

Added traffic update capability to Ixload TG

Allow yardstick to update IP/MAX of Net traffic

- Implemented functionality for updating traffics IP/MAC address
  in ixloadconfiguration.
- Extended http_ixload.py with functions for update IP/MAC
  address of netTraffic.
- In HTTP-vFW_IPv4_2Ports_Concurrency.rxf changed name's of
  networks from "client network" to "uplink_0 and the same for
  server

JIRA: YARDSTICK-1418

Change-Id: I28ef68b77466fff15af589954e3ef63e8099428f
Signed-off-by: Myron Sosyak <myronx.sosyak@intel.com>
Signed-off-by: Taras Chornyi <tarasx.chornyi@intel.com>