client::ConnectionImpl used to contain a FailoverListener to subscribe
for updates on the amq.failover exchange. This caused some lifecycle
issues including memory leaks.
Now FailoverListener is a public API class that the user must create
associated with a session to get known-broker updates.
Removed the weak_ptr logic in client::SessionImpl which was only
required because of FailoverListener.
Made SessionImpl::close() idempotent. Gets rid of spurious warning
messages in some tests.
git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk/qpid@829931 13f79535-47bb-0310-9956-ffa450edef68