Some scripts bin\*.cmd pollutes environment variables in Windows.

Some scripts (bin*.cmd) pollutes environment variables in Windows.
For example, when we execute bin\spark-submit.cmd, we will found that our command prompt keeps environment variables like %SPARK_HOME%, %SPARK_SUBMIT_DEPLOY_MODE%, and so on.
Those environment variables are only used in the script internally, so we'd better to avoid polluting the environment.