- try to detect a recent logrotate version which supports the 'su'
directive (added in 3.8.0, see
5be96cf182 (diff-e4eb329834da3d36278b1b7d943b3bc9R6))
- if logrotate can't be found, assume an old version is used
- allow the parameter to be forced by the user
fixes#9249
Signed-off-by: Gunnar Beutner <gunnar@beutner.name>