SPARK-2241: quote command line args in ec2 script

To preserve quoted command line args (in case options have space in them).

Author: Ori Kremer <ori.kremer@gmail.com>

Closes #1169 from orikremer/quote_cmd_line_args and squashes the following commits:

67e2aa1 [Ori Kremer] quote command line args
(cherry picked from commit 9fc373e3a9a8ba7bea9df0950775f48918f63a8a)

Signed-off-by: Patrick Wendell <pwendell@gmail.com>