Fixed backing up a resolv.conf symlink when it's path is relative

Added an os.chdir('/etc') then fed the value of os.readlink('/etc/resolv.conf') into os.path.abspath() and changed back to the old working dir. This fixes an issue where the backed up symlink points to the wrong location eg: ../run/resolvconf/resolv.conf which works from /etc but not from /var/wicd/ it points to /var/run/resolvconf/resolv.conf