spark-env.sh: comment out some env stuff for now

Currently using a conf file for some stuff.  Not going to set
SPARK_EXECUTOR_MEMORY etc this way.

Signed-off-by: Colin Patrick McCabe <cmccabe@cloudera.com>
set yarn.nodemanager.local-dirs to a 10-drive config

Set yarn.nodemanager.local-dirs to a 10-drive config, to avoid being
bottlenecked on a single drive's throughput.

Signed-off-by: Colin Patrick McCabe <cmccabe@cloudera.com>