aiaiai-diff-log-helper: explicitely call out python2

aiaiai-diff-log-helper: explicitely call out python2

Since this script is not a python3 script, (it runs in python2!) then we
shouldn't rely on "/usr/bin/env python" to always land us on a python2
installation, as some machines may have installed python3, and
configured their default python to be the python3 executable.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>