[repo] fix extid2entity to ensure connection's has a cnxset
else we'll call source.doexec, which attempt to access to cnxset.cu, and crash
in some case (eg unittest_cwxmlparser in sobjects/test).
Also, manually switch to 'write' mode to ensure cnxset is not released until
commit/rollback when some entity is inserted.
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