_Performance Testing issues_

Branch: dpdk-next-net

0c22daa3beaa074fd96250a15e1df1f3417670dc --> performance testing fail

Test environment and result as below:

Ubuntu 18.04
Kernel: 4.15.0-generic
Compiler: gcc 7.4
NIC: Intel Corporation Ethernet Converged Network Adapter 82599ES 10000 Mbps
Target: x86_64-native-linuxapp-gcc
Fail/Total: 0/2

Detail performance results: 
+------------+---------+----------+-------------+------------------------------+
| frame_size | txd/rxd | num_cpus | num_threads |  throughput difference from  |
|            |         |          |             |           expected           |
+============+=========+==========+=============+==============================+
| 64         | 512     | 1        | 1           | 0.41277%                     |
+------------+---------+----------+-------------+------------------------------+
| 64         | 2048    | 1        | 1           | -0.58294%                    |
+------------+---------+----------+-------------+------------------------------+

Ubuntu 18.04
Kernel: 4.15.0-generic
Compiler: gcc 7.4
NIC: Intel Corporation Ethernet Converged Network Adapter XL710-QDA2 40000 Mbps
Target: x86_64-native-linuxapp-gcc
Fail/Total: 1/2

Detail performance results: 
+------------+---------+----------+-------------+------------------------------+
| frame_size | txd/rxd | num_cpus | num_threads |  throughput difference from  |
|            |         |          |             |           expected           |
+============+=========+==========+=============+==============================+
| 64         | 512     | 1        | 1           | 2.32043%                     |
+------------+---------+----------+-------------+------------------------------+
| 64         | 2048    | 1        | 1           | -2.08141%                    |
+------------+---------+----------+-------------+------------------------------+

To view detailed results, visit:
https://lab.dpdk.org/results/dashboard/tarballs/15788/

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