This is needed because broadcast values are broken on pyspark on Mesos, it tries to import pyspark but can't, as the PYTHONPATH is not set due to changes in ff5be9a4

https://issues.apache.org/jira/browse/SPARK-1725

Author: Bouke van der Bijl <boukevanderbijl@gmail.com>

Closes #651 from bouk/include-spark-config-in-mesos-executor and squashes the following commits:

b2f1295 [Bouke van der Bijl] Inline PYTHONPATH in spark-executor
eedbbcc [Bouke van der Bijl] Include the sbin/spark-config.sh in spark-executor