Update python depdency and remove obsolete selinux xml gen code.

Bug: 18909468
Change-Id: I5f2d35942db5b21a446c4e06185bb116d0dee043
diff --git a/tools/selinux/SELinuxNeverallowTestGen.py b/tools/selinux/SELinuxNeverallowTestGen.py
index 9cb1e24..bc775d6 100755
--- a/tools/selinux/SELinuxNeverallowTestGen.py
+++ b/tools/selinux/SELinuxNeverallowTestGen.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 
 import re
 import sys