QPID-6118: Add qmf shutdown command to the broker

QMF shutdown command implemented on broker.
- ACL to control shutdown: acl deny all access method name=shutdown
- Added "qpid-config shutdown" command to shut down the broker.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1627811 13f79535-47bb-0310-9956-ffa450edef68