zdtm.py: specify python version

Otherwise it may suck on some distros (Arch i.e):
make zdtm
make[2]: Entering directory '/home/japdoll/tools/criu/test'
./zdtm.py run -a --parallel 2
  File "./zdtm.py", line 33
    print "        ..."
                      ^
SyntaxError: Missing parentheses in call to 'print'
Makefile:25: recipe for target 'zdtm' failed
make[2]: *** [zdtm] Error 1
make[2]: Leaving directory '/home/japdoll/tools/criu/test'
Makefile:9: recipe for target 'all' failed
make[1]: *** [all] Error 2
make[1]: Leaving directory '/home/japdoll/tools/criu/test'
Makefile:258: recipe for target 'test' failed
make: *** [test] Error 2
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

test/zdtm.py

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