Fix the unexpected keyword argument exceptionw when lb is enabled

opencontrail.loadbalancer.loadbalancer_db.LoadBalancerPluginDb is
creating an object of VncApi with auth_type as argument which is
an invalid argument

Change-Id: I6e4eea35b9ba56e6e113e826c8c09ecb61eedf5a
Closes-bug: #1375850