During resolv.conf update, old 'search' lines are cleared but '\n' is not
deleted, leaving behind a new blank line on every update.
This adds 's' flag to regexp, so '\n' is included in the match and deleted when
old lines are cleared.
Also, insert missing `\n` when updated 'search' line is appended to resolv.conf.
Signed-off-by: Renato Aguiar <renato@renatoaguiar.net>