test/flow_classify: enable multi-sockets system

test/flow_classify: enable multi-sockets system

This commit fixes failures of the flow_classify_autotest when
ran on dual-socket servers, as the sample application does not
support more than a single socket. Increasing the NB_SOCKETS
value allows the test to run successfully.

Fixes: 9c9befea4f57 ("test: add flow classify unit tests")
Cc: stable@dpdk.org
Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com>
Tested-by: Ferruh Yigit <ferruh.yigit@intel.com>
Tested-by: Bernard Iremonger <bernard.iremonger@intel.com>
Acked-by: Bernard Iremonger <bernard.iremonger@intel.com>