[session] make session lock reentrant
We are going to use it for other session related business. It is renamed from
_closed_lock to _lock in the same move.
#! /bin/sh -e#if [ "$1" = remove -o "$1" = upgrade ]; then if which install-docs >/dev/null 2>&1; then install-docs -r cubicweb-doc fifi#DEBHELPER#exit 0