increase failure information for ip_regex test

It's basically completely impossible to understand why this test would
fail because there is not enough post mortem information. Probably an
address didn't allocate, but this is so stripped down you'd never know
that.

Add further dump on failure to make it possible to see what's happening.

Change-Id: I536f78c77df992dde5efd22b1d763715e33f0769
Related-Bug: #1481715
diff --git a/tempest/api/compute/servers/test_list_server_filters.py b/tempest/api/compute/servers/test_list_server_filters.py
index a75cb3e..6160844 100644
--- a/tempest/api/compute/servers/test_list_server_filters.py
+++ b/tempest/api/compute/servers/test_list_server_filters.py
@@ -305,12 +305,20 @@
             params = {'ip': ip}
         else:
             params = {'ip6': ip}
+        # capture all servers in case something goes wrong
+        all_servers = self.client.list_servers(detail=True)
         body = self.client.list_servers(**params)
         servers = body['servers']
 
-        self.assertIn(self.s1_name, map(lambda x: x['name'], servers))
-        self.assertIn(self.s2_name, map(lambda x: x['name'], servers))
-        self.assertIn(self.s3_name, map(lambda x: x['name'], servers))
+        self.assertIn(self.s1_name, map(lambda x: x['name'], servers),
+                      "%s not found in %s, all servers %s" %
+                      (self.s1_name, servers, all_servers))
+        self.assertIn(self.s2_name, map(lambda x: x['name'], servers),
+                      "%s not found in %s, all servers %s" %
+                      (self.s2_name, servers, all_servers))
+        self.assertIn(self.s3_name, map(lambda x: x['name'], servers),
+                      "%s not found in %s, all servers %s" %
+                      (self.s3_name, servers, all_servers))
 
     @test.idempotent_id('67aec2d0-35fe-4503-9f92-f13272b867ed')
     def test_list_servers_detailed_limit_results(self):