dpdk: fix coverity issue
dpdk: fix coverity issue

Type: fix

This patch fixes the following DPDK plugin issue:

CID 253333:  Control flow issues  (DEADCODE)

The change also includes some cosmetic changes for error
handling.

Signed-off-by: Fan Zhang <b46d470dc79aa6fd718cd24d07380f6203b7fc3c@intel.com>
Change-Id: I830020bc3ae9a508f3a905f78333fa3ae25ce784

FDio/vpp,FDio/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp