[server] Only register "clean_sessions" looping tasks if repository has a tasks manager This prepares for calling Repository's _prepare_startup() in bootstrap() so that repository instances without a tasks manager running can still have their 'server_startup' hooks triggered (this is particularly useful for BFSS storages).

version=3
opts=uversionmangle=s/(rc|a|b|c)/~$1/ \
https://pypi.debian.net/cubicweb/cubicweb-(.+)\.(?:zip|tgz|tbz|txz|(?:tar\.(?:gz|bz2|xz)))