QPID-4502: Apply review comments from Robbie Gemmell

merge from https://svn.apache.org/repos/asf/qpid/trunk/qpid/doc/book/src/java-broker@1425665


git-svn-id: https://svn.apache.org/repos/asf/qpid/branches/0.20@1431970 13f79535-47bb-0310-9956-ffa450edef68