Reintroduce strict regex for extra_dhcp_opt test

This is partial revert of [1]. The issue got triggered
as by default dhcp_domain is set to 'novalocal' in nova and
dhclient includes that local domain when setting up
resolv.conf as part of [2].

To have predictable domain only derived as part of
neutron configuration the job unset's dhcp_domain in
nova conf.

[1] https://review.opendev.org/c/x/whitebox-neutron-tempest-plugin/+/904331
[2] https://bugzilla.redhat.com/show_bug.cgi?id=637763

Change-Id: Id5966cc7447a688ad1a1a8800993096d18f29194

whitebox_neutron_tempest_plugin/tests/scenario/test_extra_dhcp_opts.py

@@ -241,11 +241,7 @@ class ExtraDhcpOptionsTest(base.BaseTempestTestCase):
         # ipv4.domain is expected
         vm_resolv_conf = vm_ssh_client.exec_command(
             "sudo dhclient && cat /etc/resolv.conf")
-        # (rsafrono) for some reason with devstack there is sometimes one more
+        self.assertIsNotNone(re.search(r'^search\s+{}$'.format(domain_value),
-        # entry in the 'search' line, a char 'n' before the end of the line
-        # causing the test to fail. Changing the regex to be less stict
-        # in order to unblock the gates.
-        self.assertIsNotNone(re.search(r'^search\s+{}\s+'.format(domain_value),
                                        vm_resolv_conf,
                                        re.MULTILINE))
 

zuul.d/master_jobs.yaml

@@ -184,6 +184,9 @@
           $NEUTRON_DHCP_CONF:
             agent:
               availability_zone: nova
+          $NOVA_CONF:
+            api:
+              dhcp_domain: ''
         test-config:
           $TEMPEST_CONFIG:
             neutron_plugin_options: