Add keystone client optional arg tests

Make sure optional arguments don't break

Add tests for:
--version
--debug
--timeout

Change-Id: Ib71cfca1e757c26e6311b060faf5185df6391a43
diff --git a/tempest/cli/simple_read_only/test_keystone.py b/tempest/cli/simple_read_only/test_keystone.py
index 067f58c..45d519b 100644
--- a/tempest/cli/simple_read_only/test_keystone.py
+++ b/tempest/cli/simple_read_only/test_keystone.py
@@ -107,3 +107,14 @@
 
     def test_admin_bashcompletion(self):
         self.keystone('bash-completion')
+
+    # Optional arguments:
+
+    def test_admin_version(self):
+        self.keystone('', flags='--version')
+
+    def test_admin_debug_list(self):
+        self.keystone('catalog', flags='--debug')
+
+    def test_admin_timeout(self):
+        self.keystone('catalog', flags='--timeout 15')