https://issues.apache.org/jira/browse/SPARK-7945

Now applications submited by org.apache.spark.launcher.Main read properties file without doing trim to values in it.
If user left a space after a value(say spark.driver.extraClassPath) then it probably affect global functions(like some jar could not be included in the classpath), so we should do it like Utils.getPropertiesFromFile.

Author: WangTaoTheTonic <wangtao111@huawei.com>
Author: Tao Wang <wangtao111@huawei.com>

Closes #6496 from WangTaoTheTonic/SPARK-7945 and squashes the following commits:

bb41b4b [Tao Wang] indent 4 to 2
6dd1cf2 [WangTaoTheTonic] use a simpler way
2c053a1 [WangTaoTheTonic] Do trim to values in properties file