python: specify python2 as .py interpreter

On some distro the default python interpreter is Python 3,
which results in such errors:
>  Running zdtm/static/socket-tcp-closed.hook(--post-start)
>  make[1]: Nothing to be done for default.
>  ./socket-tcp-closed --pidfile=socket-tcp-closed.pid --outfile=socket-tcp-closed.out
>    File "zdtm/static/socket-tcp-closed.hook", line 16
>      except OSError, e:
>                    ^
>  SyntaxError: invalid syntax
>  ######### Test zdtm/static/socket-tcp-closed FAIL at hook --post-start #########
>  Running zdtm/static/socket-tcp-closed.hook(--clean)
>    File "zdtm/static/socket-tcp-closed.hook", line 16
>      except OSError, e:
>                    ^
>  SyntaxError: invalid syntax
>  Traceback (most recent call last):
>    File "zdtm.py", line 1921, in <module>
>      do_run_test(tinfo[0], tinfo[1], tinfo[2], tinfo[3])
>    File "zdtm.py", line 1388, in do_run_test
>      try_run_hook(t, ["--clean"])
>    File "zdtm.py", line 1053, in try_run_hook
>      raise test_fail_exc("hook " + " ".join(args))
>  __main__.test_fail_exc: <__main__.test_fail_exc instance at 0x76294468>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

coredump/criu-coredump

-#!/usr/bin/env python
+#!/usr/bin/env python2
 import argparse
 import os
 

crit/crit

-#!/usr/bin/env python
+#!/usr/bin/env python2
 import argparse
 import sys
 import json

lib/py/images/images.py

-#!/bin/env python
+#!/bin/env python2
 
 # This file contains methods to deal with criu images.
 #

scripts/magic-gen.py

-#!/bin/env python
+#!/bin/env python2
 import os, sys
 import struct
 

test/check_actions.py

-#!/usr/bin/env python
+#!/usr/bin/env python2
 
 import sys
 import os

test/others/ext-tty/run.py

-#!/usr/bin/env python
+#!/usr/bin/env python2
 import subprocess
 import os, sys, time, signal, pty
 

test/zdtm/static/socket-tcp-fin-wait1.hook

-#!/usr/bin/env python
+#!/usr/bin/env python2
 import sys
 
 sys.path.append("../crit")