Switch from OVN metadata agent to OVN agent

this update was missing from a previous commit, it fixes the two-node jobs

Change-Id: Id0b732d36b149364eaf34a0ddb05305cdf223d94
Signed-off-by: Gregory Thiemonge <gthiemon@redhat.com>

zuul.d/jobs.yaml

@@ -430,7 +430,7 @@
           q-dhcp: false
           q-l3: false
           q-meta: false
-          q-ovn-metadata-agent: true
+          q-ovn-agent: true
 
 - job:
     name: octavia-dsvm-noop-base