- OODT-726: make FilterTask more robust (found through testing XDATA)
  - if Rename_[Key] to a key that already was provided in Metadata, task would add to that metadata key's value list, instead of replacing it.
  - intended behavior is to replace
  - added test to expose the issue
  - fixed by using metadata.replaceMetadata instead of metadata.addMetadata

git-svn-id: https://svn.apache.org/repos/asf/oodt/trunk@1615380 13f79535-47bb-0310-9956-ffa450edef68