Use /usr/bin/env python to autodetect python

https://review.openstack.org/#/c/564024/ used
/bin/python as the shebang but this can be different
for different platforms, switch to /usr/bin/env to
handle it.

Also update undercloud_ctlplane_network.py to use
/usr/bin/env for consistency, although this file
is not executable.

Change-Id: Id915ded03ae5a471ffa2dca13e2da90021279f63

extraconfig/post_deploy/undercloud_ctlplane_network.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 
 import json
 import netaddr

extraconfig/tasks/instanceha/check-run-nova-compute

@@ -1,4 +1,4 @@
-#!/bin/python -utt
+#!/usr/bin/env python -utt
 
 import os
 import sys