Raise the timeout of "neutron-ovn-rally-task" to 9000

Closes-Bug: #2022070
Change-Id: Iffab13b68bcd875cf3d3d1db2be2d44d96bf3663
(cherry picked from commit b6ce722)

Author: ralonsoh

zuul.d/rally.yaml

@@ -177,5 +177,5 @@
             openstack:
               neutron_bind_l2_agent_types: "OVN Controller Gateway agent"
       rally_task: rally-jobs/task-neutron.yaml
-    timeout: 7800
+    timeout: 9000