Updated Qpid client to 0.20 and added HTTP management plugin configuration
Merge pull request #491 from grkvlt/qpid

Fix QpidIntegrationTest
Tolerate multiple calls to entity.manage()

- Instead of exception, just warn and ignore.
- Required because on rebind if a policy creates an entity while still
  rebinding other entities (while calling onManagementStarting on each),
  then when iterating over all to call onManagementStarted it will fail
  if one of those referenced entities is already fully managed.