By adding a logger field to "prog" struct, and use this field inside its
method instead of always accessing global mainLog variable. This at
least ensure more consistent usage of the logger during ctrld prog
runtime, and also help refactoring the code more easily in the future
(like replacing the logger library).
Fixes search domains not being preserved when the resolv.conf file is
reverted to its previous state. This ensures that important domain
search configuration is maintained during DNS configuration changes.
The search domains handling was missing in setResolvConf function,
which is responsible for restoring DNS settings.
Cuong Manh Le