EC2 script should exit with non-zero code on UsageError

This is specially import because some ssh errors are raised as UsageError, preventing an automated usage of the script from detecting the failure.

Author: Allan Douglas R. de Oliveira <allan@chaordicsystems.com>

Closes #638 from douglaz/ec2_exit_code_fix and squashes the following commits:

5915e6d [Allan Douglas R. de Oliveira] EC2 script should exit with non-zero code on UsageError
SPARK-1710: spark-submit should print better errors than "InvocationTargetException"

Catching the InvocationTargetException, printing getTargetException.

Author: Sandeep <sandeep@techaddict.me>

Closes #630 from techaddict/SPARK-1710 and squashes the following commits:

834d79b [Sandeep] changes from srowen  suggestions
109d604 [Sandeep] SPARK-1710: spark-submit should print better errors than "InvocationTargetException"