Ensure HttpExchange notified when HttpConnection close is called

This fix to org.mortbay.jetty.client.HttpConnection ensured that if close() was called with an Exchange outstanding,
the Exchange was notified immediately:

r5338 | janb | 2009-07-29 10:57:04 +1000 (Wed, 29 Jul 2009) | 2 lines

Ensure exception on close is reported to the Exchange if there is one.

That code appears to have been removed by this checkin:

r5636 | gregw | 2009-10-17 09:11:51 +1100 (Sat, 17 Oct 2009) | 6 lines

289221 HttpExchange does not timeout when using blocking connector
290761 HttpExchange.waitForDone()
291340 state==HEADER (Race condition in onException() notifications)

A use-case where this is a problem is the BayeuxClient. If the HttpClient that the BayeuxClient uses is stopped, and thus all the HttpConnections stopped, the BayeuxClient's log poll HttpExchange is not notified and hence does not detect the connect failure.

Note that if the entire HttpClient was not stopped, but rather a single HttpConnection is stopped, then eventually presumably the timeout would expire (default is 5mins) and the HttpExchange would be notified then.