Transparent support for FIF inputs including intermediate outputs as source of HashJoin
1. During planning record cascading.tap.hadoop.cached.<tapid>=inputPathCSV
   for hash join tap
   Set the tap source to cdcfs:/<tapid>

2. Prior to submitting FlowStep jobs, check whether DistributedCache needs to be populated
   by inspecting all taps.
   for each original input <pathUri>, create a DC entry
     <pathUri>#<tapid>-cdcfs-<symlinkUUID>

3. On the server side, when mapper calls getSplits on cdcfs:/<tapid>, all
   localized files in DC that match whose symlink matches <tapid>-cdcfs-*
   are returned.

For easier review moved all the logic to
cascading/tap/hadoop/fs/DistributedCacheFileSystem.java