remove the sshsessid when shuting down agents etc

tes/apiendpoints.py

@@ -93,6 +93,7 @@ class SSHAgent(Resource):
             sshsess = SSHSession.get_sshsession()
             sshsess.kill()
             SSHSession.remove_sshsession()
+            session.pop('sshsessid', None)
             return []
         except Exception as e:
             import traceback