QPID-6093: Address code review comments:
1) Display promptMessages in edit broker dialog
2) Fix issue with button disaperaing on dialog resize on editing VH/VHN and broker
3) Fix context name/value pair editing in Safari
4) Stop posting form data on pressing Cancel button in dialogs for editing VH/VHN and broker

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1625650 13f79535-47bb-0310-9956-ffa450edef68