Do not use slapos.cookbook recipe during installation.
Install slapos-cookbook section from slapos stack.

This automatically handle lxml installation.
Merge branch 'erp5'
Merge branch 'master' into erp5-component
version up : MariaDB 5.5.32.
increase nuke_limit to prevent 503 error 'FetchError   c Could not get storage'.
Allow to use crontab without root user.
Remove setuid bit on crontab.
Merge branch 'master' into erp5-component
Merge branch 'erp5-component' into erp5