Explicitly use python2 for poller-wrapper.py

Currently the "interpreter" for the poller-wrapper.py is "python". Since more and more distros use python3 as default and this wrapper is not (yet) python3-compatible, this leads poller to stop working.

So as long as poller-wrapper.py is not python3 compatible (it is not only that print-command is not in braces, it's also using no longer existing mysql-bindings) it might be a good idea to actually use

#! /usr/bin/env python2

as firstline, as this symlink should exist always (at least as long as there is a python2-interpreter installed).

BR
Jens