Run Hadoop tutorial binaries from within build dir.

Review: https://reviews.apache.org/r/11109
Build fix for HadoopPipes.cc with GCC 4.7.

Review: https://reviews.apache.org/r/11113
Hadoop tutorial version bump (CDH4.2.0 -> 4.2.1).

Review: https://reviews.apache.org/r/11120