bugfix: Remove dependency on ifconfig

bugfix: Remove dependency on ifconfig

VSPERF uses ifconfig at several places to bring up
a networking interface. However ifconfig has been
deprecated by iproute2 package and it is not available
in standard installation of many Linux distributions.
Thus all calls of ifconfig have been replaced by
call of 'ip' tool.

Change-Id: I935eaf85b6082e4641d12cffea3e0882c634e5ea
JIRA: VSPERF-299
Signed-off-by: Martin Klozik <martinx.klozik@intel.com>
Reviewed-by: Maryam Tahhan <maryam.tahhan@intel.com>
Reviewed-by: Al Morton <acmorton@att.com>
Reviewed-by: Christian Trautman <ctrautma@redhat.com>
Reviewed-by: Brian Castelli <brian.castelli@spirent.com>