[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).
Document: cubicweb-doc
Title: CubicWeb Documentation
Author: Logilab
Abstract: Some base documentation for CubicWeb users and developpers
Section: Apps/Programming
Format: HTML
Index: /usr/share/doc/python-cubicweb-documentation/html/index.html
Files: /usr/share/doc/python-cubicweb-documentation/html/*