When running "make lcitool-refresh", this currently uses the hard-coded
/usr/bin/python3 from the script's shebang line for running Python.
That's bad, since neither /usr/bin/python3 is guaranteed to exist, nor
does it honor the python interpreter that the user might have chosen
while running the "configure" script. Thus let's rather use $(PYTHON)
in the Makefile, and improve the shebang line in the script in case
someone runs this directly.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20220329063958.262669-1-thuth@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>