Sending OFPPortStatsRequest() message fails for dpdk-type port of ovs.

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Config:

• ovs version 2.13
• dpdk version: 19.11.10
• NIC: e1000
• operation system: ubuntu 18.01

Problem:

Analyze:
When I send OFPPortStatsRequest() to ovs, I get a error from struct.uppack_from(). After analyzed, I found that the reason is in fucntion OFPPropCommonExperimenter4ByteData.parser() at ofproto_v1_4_parse.py:939, which unpack message by 4 bytes but dpdk-type portstatsreply message is not a multiple of 4.