[querier] test and fix potential bug in insertion query with multiple relations inside, caused by a name conflict. Also fix another bug non reproduced by using a set instead of a list (list may leads to compare entity instances which isn't allowed).

usr/lib/python2.4/site-packages/cubicweb/
etc/init.d
etc/cubicweb.d
etc/bash_completion.d
usr/bin
usr/share/doc/cubicweb-ctl
var/run/cubicweb
var/log/cubicweb
var/lib/cubicweb/backup
var/lib/cubicweb/instances