Re Reduce number of routers created in test_gateway_chassis_rebalance

Was originally reduced in [1] but got restored in [2] during rebase.
This patch re applies it.

[1] https://review.opendev.org/c/openstack/neutron/+/874765
[2] https://review.opendev.org/c/openstack/neutron/+/874760

Related-Bug: #2007353
Signed-off-by: Yatin Karel <[email protected]>
Change-Id: I5765b32d6d33eda88ab0206e75e57b67a4afc4b5
(cherry picked from commit f7e0561)

Author: karelyatin

neutron/tests/functional/services/ovn_l3/test_plugin.py

@@ -791,7 +791,7 @@ def test_gateway_chassis_rebalance(self):
         # Tries to create 5 routers with a gateway. Since we're using
         # physnet4, the chassis candidates will be chassis4 initially.
         num_routers = len(self._create_routers_wait_pb(
-            1, 20, gw_info=gw_info, bind_chassis=chassis4))
+            1, 5, gw_info=gw_info, bind_chassis=chassis4))
         self.l3_plugin.schedule_unhosted_gateways()
         expected = {chassis4: {1: num_routers}}
         self.assertEqual(expected, self._get_gwc_dict())