use distributed cache for the replicated data set in FR join

                 Key: PIG-872
             Project: Pig
          Issue Type: Improvement
            Reporter: Olga Natkovich

Currently, the replicated file is read directly from DFS by all maps. If the 
number of the concurrent maps is huge, we can overwhelm the NameNode with open 

Using distributed cache will address the issue and might also give a 
performance boost since the file will be copied locally once and the reused by 
all tasks running on the same machine.

The basic approach would be to use cacheArchive to place the file into the 
cache on the frontend and on the backend, the tasks would need to refer to the 
data using path from the cache.

Note that cacheArchive does not work in Hadoop local mode. (Not a problem for 
us right now as we don't use it.)

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