JENA-439
Catch QueryCancelledException and send 503, not 408.

git-svn-id: https://svn.apache.org/repos/asf/jena/trunk@1469051 13f79535-47bb-0310-9956-ffa450edef68
Comments about timeouts

git-svn-id: https://svn.apache.org/repos/asf/jena/trunk@1469052 13f79535-47bb-0310-9956-ffa450edef68