[SPARK-7512] [SPARKR] Fix RDD's show method to use getJRDD
[SPARK-7512] [SPARKR] Fix RDD's show method to use getJRDD

Since the RDD object might be a Pipelined RDD we should use `getJRDD` to get the right handle to the Java object.

Fixes the bug reported at
http://stackoverflow.com/questions/30057702/sparkr-filterrdd-and-flatmap-not-working

cc concretevitamin

Author: Shivaram Venkataraman <ad63b47dfac1951bde2b661ba9fbbe123f686bee@cs.berkeley.edu>

Closes #6035 from shivaram/sparkr-show-bug and squashes the following commits:

d70145c [Shivaram Venkataraman] Fix RDD's show method to use getJRDD Fixes the bug reported at http://stackoverflow.com/questions/30057702/sparkr-filterrdd-and-flatmap-not-working

(cherry picked from commit 0835f1edd4c9c05439df85c248faf6787d45f7b7)
Signed-off-by: Shivaram Venkataraman <ad63b47dfac1951bde2b661ba9fbbe123f686bee@cs.berkeley.edu>

andrewor14/iolap,andrewor14/iolap,andrewor14/iolap,andrewor14/iolap,andrewor14/iolap,andrewor14/iolap,andrewor14/iolap