Enable bridge flows and tcpdump in tempest multinode

Enable br-int-flows and br-ex-tcpdump services in
tempest-multinode-full-py3 job, these will help in
debugging network issues.

Related-Bug: #1998916
Change-Id: I947a6e2a88d7ad38cc00aa694438cb3101030168
diff --git a/zuul.d/integrated-gate.yaml b/zuul.d/integrated-gate.yaml
index c44a2b2..2c720d9 100644
--- a/zuul.d/integrated-gate.yaml
+++ b/zuul.d/integrated-gate.yaml
@@ -246,10 +246,15 @@
         neutron: https://opendev.org/openstack/neutron
       devstack_services:
         neutron-trunk: true
+        br-ex-tcpdump: true
+        br-int-flows: true
     group-vars:
       subnode:
         devstack_localrc:
           USE_PYTHON3: true
+        devstack_services:
+          br-ex-tcpdump: true
+          br-int-flows: true
 
 - job:
     name: tempest-slow