Update qpid attributes

This change finishes off bp use-data-bag-for-qpid-password by removing
the unnecessary qpid attribute and defaulting qpid username to the same
value as openstack.mq.user.

Change-Id: I3ee99989c54fcda746eacb5c38011308494dc394
Implements: blueprint use-data-bag-for-qpid-password
Merge "Update qpid attributes"