Fixes #3324 : Do not to produce an invalid sudoers file when a command was specified.

Signed-off-by: Nicolas Charles <nicolas.charles@normation.com>
Fixes #3323 : Do not insert env_reset setting if it already exists in sudoers.

Signed-off-by: Nicolas Charles <nicolas.charles@normation.com>
Merge branch 'branches/rudder/2.3' into branches/rudder/2.4
Merge branch 'branches/rudder/2.4' into branches/rudder/2.5