Fix test_rpc_consumer_isolation for oslo.messaging 5.31.0
Fix test_rpc_consumer_isolation for oslo.messaging 5.31.0

With this change in oslo.messaging 5.31.0:

  I0bbf9fca0ecbe71efa87c9613ffd32eb718f2c0e

The endpoint passed in is going to be checked for a 'target'
attribute and check it's type if set, so looking for it has
to be ignored.

Change-Id: Ic022bdc0291ce1498abdfe1acd3cc51adf7db7c6
Closes-Bug: #1715470

phenoxim/cinder,mahak/cinder,j-griffith/cinder,mahak/cinder,Datera/cinder,eharney/cinder,openstack/cinder,Datera/cinder,phenoxim/cinder,eharney/cinder,openstack/cinder,j-griffith/cinder