examples/l3fwd-vf: fix race condition
examples/l3fwd-vf: fix race condition

When the routing is through the same queue, the app crashed.

Signed-off-by: Daniel Mrzyglod <998f22cc3a6ac3535545292178d834b83a4e2a87@intel.com>
Acked-by: Neil Horman <3316dc2d77df57653443c0391a5296176d6ca9c3@tuxdriver.com>

msune/dpdk,mixja/dpdk,john-mcnamara-intel/dpdk,venkynv/dpdk-mirror,mixja/dpdk,msune/dpdk,john-mcnamara-intel/dpdk,venkynv/dpdk-mirror,tsphillips/dpdk-fork,msune/dpdk,venkynv/dpdk-mirror,mixja/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,msune/dpdk,tsphillips/dpdk-fork,mixja/dpdk,venkynv/dpdk-mirror,tsphillips/dpdk-fork,tsphillips/dpdk-fork