pkt_gen: support of standalone execution of traffic generator

pkt_gen: support of standalone execution of traffic generator

Support for multiple modes of VSPERF operation has been added.
These modes can be used for standalone execution of traffic
generator or for manual testing or for execution of unsupported
traffic generator. Supported modes are: "normal" - execute vSwitch,
VNF and traffic generator; "trafficgen" - execute only traffic
generator; "trafficgen-off" - execute vSwitch and VNF.
Normal mode is selected by default.
In case that trafficgen mode is selected, then various
--test-params could be specified to affect traffic generator
configuration. These parameters include traffic type, frame rate,
bidirectional and scalability settings. Selection of transport
protocol is not supported by IxNet yet (UDP is enforced), thus
modification of transport protocol from command line is not
supported too.
Fixes of testpmd and qemu warning patches are inclduded.

Change-Id: Idac10fe03e724075268a01ec3eb0817fba830aec
JIRA: VSPERF-173
Signed-off-by: Martin Klozik <martinx.klozik@intel.com>
Reviewed-by: Maryam Tahhan <maryam.tahhan@intel.com>
Reviewed-by: Al Morton <acmorton@att.com>