OPENDJ-1870 CR-6581 Update BackupManager to generic tool

Nicolas Capponi

27.20.2015 75fceea66e311b3de58d76a4c993af0fec13dd3d

opendj-server-legacy/src/main/java/org/opends/server/backends/pluggable/BackupManager.java does not exist in tree b0f5a5d192996be57de58327ed182b8f50770d6a