msg/async: bump dpdk to v16.07

as some distros include it already. so sync it up to avoid building
failures on them with dpdk-dev package(s) shipped by distro.

Signed-off-by: Kefu Chai <kchai@redhat.com>

diff --git a/src/dpdk b/src/dpdk
index a38e5ec15e3fe615b94f3cc5edca5974dab325ab..20e2b6eba13d9eb61b23ea75f09f2aa966fa6325 160000 (submodule)
--- a/src/dpdk
+++ b/src/dpdk
@@ -1 +1 @@
-Subproject commit a38e5ec15e3fe615b94f3cc5edca5974dab325ab
+Subproject commit 20e2b6eba13d9eb61b23ea75f09f2aa966fa6325