The need for this change stems from following issues:
1) When ovs_use_veth = False with ovs-dpdk issue with ovs
was observed - after vswitch restart interface is not comming up.
Meaning ovs-dpdk uses ovs internal ports and it is not able to bring
them up on restart.
2) When ovs_use_veth = True and ovs-dpkd is used, packets sent with
incorrect checksum due to the fact that ovs-dpdk does not do checksum
calculations for veth interface.
This commit allows to use second option and resolve checksum issue by
disabling checksum offload.
Closes-Bug: #1832021
Related-Bug: #1831935
Change-Id: Iecce8d2c6c2c46718cc1020c6e8f914cd4560e4b
(cherry picked from commit 11838a2bc5)