Fix py35 test failure
Fix py35 test failure

dict.keys() returns object dict_keys on Python 3, can't work well
with kombu recently, convert it to list before futhur processing.

Closes-Bug: #1687855
Change-Id: I9dcfadd8f16eccce06f4cde3b2a6669f28a3f8bc

openstack/taskflow,jimbobhickville/taskflow,openstack/taskflow,jimbobhickville/taskflow