[web] Stop using negative indices with os.stat results The python doc says: More items may be added at the end by some implementations. .st_mtime is also more readable than [-2].

etc/init.d
etc/cubicweb.d
etc/bash_completion.d
usr/bin
usr/share/doc/cubicweb-ctl
var/log/cubicweb
var/lib/cubicweb/backup
var/lib/cubicweb/instances