[devtools/qunit] Turn FirefoxHelper into a context manager So that stop() method always gets called. Also ensure temporary directory created on __init__ gets deleted as well upon exit.

#! /bin/sh -e

if [ -x "/etc/init.d/cubicweb-ctl" ]; then
    invoke-rc.d cubicweb-ctl restart || true
fi
 
 
#DEBHELPER#
 
exit 0