Modified syntax error in spark-submit2.cmd. Command prompt doesn't have "defined" operator.

Author: Masayoshi TSUZUKI <tsudukim@oss.nttdata.co.jp>

Closes #4428 from tsudukim/feature/SPARK-5396 and squashes the following commits:

ec18465 [Masayoshi TSUZUKI] [SPARK-5396] Syntax error in spark scripts on windows.