QPID-5423: list only the additional deps needed by the plugin, rather than its actual deps, to prevent duplication by the release package creation process.

Largely reverts the effective value of the 'broker-plugins-management-http.libs' property to its old [incorrect] state other than r1529610 for QPID-5207/QPID-5048 adding the dojo dep. Yet another example of our Ant build making the simplest things difficult.

merged from trunk r1551042


git-svn-id: https://svn.apache.org/repos/asf/qpid/branches/0.26@1551184 13f79535-47bb-0310-9956-ffa450edef68