Fixes #4798: Switch to CFEngine 3.6.0rc1 for Rudder

Co-Authored-By: Nicolas PERRON nicolas.perron@normation.com
Merge pull request #327 from Kegeruneku/ust_4798/int/4799_upgrade_to_cfengine_3_6

Fixes #4798: Switch to CFEngine 3.6.0rc1 for Rudder