[stable/train only] Pin neutron-tempest-plugin

Neutron tempest plugin recently made some incompatible
changes that adversely affect its installation in stable/train
environments. We don't need this tempest plugin in our tests,
except that neutron-dynamic-routing has a test dependency
on this by the virtue of having their tempest plugin in-tree.

This issue was fixed in the Ussuri
release: https://review.opendev.org/#/c/695014/.

Change-Id: I036d1cf637cc99428836b2cd53b335090bfa2fd5
Signed-off-by: Goutham Pacha Ravi <gouthampravi@gmail.com>

.zuul.yaml

@@ -309,9 +309,11 @@
       - openstack/manila
       - openstack/manila-tempest-plugin
       - openstack/neutron-dynamic-routing
-      # TODO(gouthamr): Remove the line below when neutron-dynamic-routing
-      # separates its tempest plugin from its tree
-      - openstack/neutron-tempest-plugin
+      # NOTE(gouthamr): Pinned to a version that works, we don't really need
+      # this plugin for our testing, we bring it in because
+      # neutron-dynamic-routing needs this until the Ussuri release
+      - name: openstack/neutron-tempest-plugin
+        override-checkout: 1.1.0
       - openstack/python-manilaclient
       - openstack/tempest
 
@@ -349,9 +351,11 @@
       - openstack/manila
       - openstack/manila-tempest-plugin
       - openstack/neutron-dynamic-routing
-      # TODO(gouthamr): Remove the line below when neutron-dynamic-routing
-      # separates its tempest plugin from its tree
-      - openstack/neutron-tempest-plugin
+      # NOTE(gouthamr): Pinned to a version that works, we don't really need
+      # this plugin for our testing, we bring it in because
+      # neutron-dynamic-routing needs this until the Ussuri release
+      - name: openstack/neutron-tempest-plugin
+        override-checkout: 1.1.0
       - openstack/python-manilaclient
       - openstack/tempest