Fix unstable assertion in test_cinder_endpoints

In simple_read_only.test_cinder.test_cinder_endpoints, the test case
assumes that the first table of 'cinder endpoints' always ['nova',
'Value']. However, it is sometimes wrong.
So in this commit, the test verifies that they have 2 or more headers
and has a 'Value' header.

Change-Id: Idb3f2ebc6b7e05178621ac3701b7c3d02e1d7591
Closes-Bug: #1363018
Closes-Bug: #1362703
diff --git a/tempest/cli/simple_read_only/volume/test_cinder.py b/tempest/cli/simple_read_only/volume/test_cinder.py
index 3a9a7a6..e44a577 100644
--- a/tempest/cli/simple_read_only/volume/test_cinder.py
+++ b/tempest/cli/simple_read_only/volume/test_cinder.py
@@ -121,8 +121,12 @@
         self.assertTableStruct(zone_list, ['Name', 'Status'])
 
     def test_cinder_endpoints(self):
-        endpoints = self.parser.listing(self.cinder('endpoints'))
-        self.assertTableStruct(endpoints, ['nova', 'Value'])
+        out = self.cinder('endpoints')
+        tables = self.parser.tables(out)
+        for table in tables:
+            headers = table['headers']
+            self.assertTrue(2 >= len(headers))
+            self.assertEqual('Value', headers[1])
 
     def test_cinder_service_list(self):
         service_list = self.parser.listing(self.cinder('service-list'))