Add a single attribute for qpid protocol

This fixes the issue that there is no single attribute for qpid protocol
attribute, I defined a ['openstack']['mq']['qpid']['protocol']
attribute and it's default value is "tcp", and for the various openstack
service's qpid protocol attribute, we can override this attribute for
all openstack service, or they can override the individual qpid protocol
for the specific openstack service

Change-Id: I4cdae33f9d3f83edbf62d5019f9cb6830a02ab83
Merge "Add a single attribute for qpid protocol"