Enhance unit test coverage: agents_client

In order to test list_agents with 100% test coverage
we also need to check the function with parameters.

Change-Id: I18b5f3aeff24b97ddd35d3ddc31334ff179829dd
diff --git a/tempest/tests/services/compute/test_agents_client.py b/tempest/tests/services/compute/test_agents_client.py
index 9493a32..01035ab 100644
--- a/tempest/tests/services/compute/test_agents_client.py
+++ b/tempest/tests/services/compute/test_agents_client.py
@@ -56,6 +56,12 @@
             'tempest.common.service_client.ServiceClient.get',
             {"agents": []},
             bytes_body)
+        self.check_service_client_function(
+            self.client.list_agents,
+            'tempest.common.service_client.ServiceClient.get',
+            {"agents": []},
+            bytes_body,
+            hypervisor="kvm")
 
     def _test_create_agent(self, bytes_body=False):
         self.check_service_client_function(