Change par file generate rules.

Make sure the shebang of the par file is consistent with the main python
script rather than use /usr/bin/python arbitrarily.

Bug: 185399398
Bug: 185094069
Test: m atest ; atest-dev --help
      m atest-py2 ; atest-py2-dev --help
Change-Id: Ice4590b3d173e6d11e608c2ca29b297df0dc4089
diff --git a/python/scripts/stub_template_host.txt b/python/scripts/stub_template_host.txt
index a48a86f..138404b 100644
--- a/python/scripts/stub_template_host.txt
+++ b/python/scripts/stub_template_host.txt
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env '%interpreter%'
 
 import os
 import re
@@ -82,7 +82,7 @@
 
     sys.stdout.flush()
     retCode = subprocess.call(args)
-    exit(retCode)
+    sys.exit(retCode)
   except:
     raise
   finally: