Remove variable part of agent dict to fix AgentManagementTest

Agents may vary their configuration while API tests blindly
compare agent dicts. Need to pop items that may change.

Change-Id: I150f4e9f2e79f6e20f18dee69cf061c68a5bed68
Closes-Bug: #1299350
diff --git a/tempest/api/network/admin/test_agent_management.py b/tempest/api/network/admin/test_agent_management.py
index 342bc6a..b848994 100644
--- a/tempest/api/network/admin/test_agent_management.py
+++ b/tempest/api/network/admin/test_agent_management.py
@@ -37,8 +37,10 @@
         agents = body['agents']
         # Hearthbeats must be excluded from comparison
         self.agent.pop('heartbeat_timestamp', None)
+        self.agent.pop('configurations', None)
         for agent in agents:
             agent.pop('heartbeat_timestamp', None)
+            agent.pop('configurations', None)
         self.assertIn(self.agent, agents)
 
     @test.attr(type=['smoke'])