Explicitely use python2

Some distributions are using python3 as the default python.
On those ones, we need to explicitely use python2.

bin/oscp

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 # vim: expandtab:tabstop=4:shiftwidth=4
 
 import argparse

bin/ossh

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 # vim: expandtab:tabstop=4:shiftwidth=4
 
 import argparse

inventory/aws/ec2.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 
 '''
 EC2 external inventory script

inventory/gce/gce.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 # Copyright 2013 Google Inc.
 #
 # This file is part of Ansible

inventory/multi_ec2.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 # vim: expandtab:tabstop=4:shiftwidth=4
 
 from time import time

test/units/mutli_ec2_test.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 
 import unittest
 import sys