Fixes #5204: Update the documation to add an upgrade part about RHEL6
Fixes #5205: Incomplete command to force inventory
Merge pull request #68 from Kegeruneku/bug_5204/int/5204_fix_upgrade_documentation_for_rpm_oses

Fixes #5204: Update the documation to add an upgrade part about RHEL6
Merge pull request #69 from peckpeck/bug_5205/incomplete_command_to_force_inventory

Fixes #5205: Incomplete command to force inventory
Merge branch 'branches/rudder/2.6' into branches/rudder/2.10

Conflicts:
	12_upgrade/20_upgrade_centos_rhel.txt
Merge branch 'branches/rudder/2.10' into branches/rudder/2.11
Fixes #5222: Write documentation to install distributed rudder