Adding qpid support to quantum

Moving all qpid parameters under default["openstack"]["network"]["mq"]["qpid"]
so that other qpid options can be added under it. Rabbit parameters
will be brought under "mq" eventually. MQ is selected through
default["openstack"]["network"]["mq"]["service_type"]. Default is
"rabbitmq".

Implements: blueprint qpid-activemq-support
Change-Id: I7ac232c52d4fcf72764c63562f58f58c1088ef65