test/kni: check module dependency

test/kni: check module dependency

Check the prerequisites to run the test
1.checked whether the rte_kni module is loaded, if not fail testcase
2.checked whether the rte_kni module is loaded with loop back mode,
  if not skip packet forwarding testcase and log
3.Disabled the test in freebsd as test is not supported

Fixes: 5233e5924a ("app/test: update kni")
Cc: stable@dpdk.org
Signed-off-by: Naga Suresh Somarowthu <naga.sureshx.somarowthu@intel.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>