Add image-list to glance cli help test

In the glance client, there is 'image-list' that is not deprecated.
So this should be added to wanted_commands.

Change-Id: Ic14a9aa1ac24a7756e390a4f6e26e3af2952a52d
diff --git a/tempest/cli/simple_read_only/test_glance.py b/tempest/cli/simple_read_only/test_glance.py
index 90cdc55..2fd8212 100644
--- a/tempest/cli/simple_read_only/test_glance.py
+++ b/tempest/cli/simple_read_only/test_glance.py
@@ -77,7 +77,7 @@
         wanted_commands = set(('image-create', 'image-delete', 'help',
                                'image-download', 'image-show', 'image-update',
                                'member-create', 'member-delete',
-                               'member-list'))
+                               'member-list', 'image-list'))
         self.assertFalse(wanted_commands - commands)
 
     # Optional arguments: