A recently introduced readiness probe for neutron-ovs-agent makes use of
an OVSDB table entry 'dpdk_initialized' which does not exist in OVS
versions preceeding v2.10.0. This patch changes the readiness probe to
exit successfully if this table entry does not exit. Thereby it does not
give any guarantees for older versions of OVS, but at least allows the
readiness probe to pass.
Change-Id: Ic77c6bdd60730c1a7c5e55fdb4afc6db938f0ddb
dddbf37c0e