Disabling Utils.chmod700 for Windows

This patch makes Spark 1.2.1rc2 work again on Windows.

Without it you get following log output on creating a Spark context:
INFO  org.apache.spark.SparkEnv:59 - Registering BlockManagerMaster
ERROR org.apache.spark.util.Utils:75 - Failed to create local root dir in .... Ignoring this directory.
ERROR org.apache.spark.storage.DiskBlockManager:75 - Failed to create any local dir.

Author: Martin Weindel <martin.weindel@gmail.com>
Author: mweindel <m.weindel@usu-software.de>

Closes #4299 from MartinWeindel/branch-1.2 and squashes the following commits:

535cb7f [Martin Weindel] fixed last commit
f17072e [Martin Weindel] moved condition to caller to avoid confusion on chmod700() return value
4de5e91 [Martin Weindel] reverted to unix line ends
fe2740b [mweindel] moved comment
ac4749c [mweindel] fixed chmod700 for Windows