really ban exitVM with security policy

[rmuir]

Today this is implicitly allowed. In tests actually we stop it, because Uwe already fixed this issue in TestSecurityManager. But nothing stops it when you are actually running ES.

See the notes in RuntimePermission[1]:

 Note: The "exitVM.*" permission is automatically granted to all code loaded from 
 the application class path, thus enabling applications to terminate themselves.

1. http://docs.oracle.com/javase/7/docs/api/java/lang/RuntimePermission.html

[rjernst]

LGTM