Add back needrestart

[daradib]

needrestart is recommended by the apt-dater-host and docker.io packages, but currently currently purged in ocf::packages. Understandably, needrestart prompts in the default interactive mode are annoying, particularly when running apt-dater. The solution is to configure automatic mode. According to @chriskuehl, in automatic mode it would restart lightdm automatically (see rt#3110), but beginning with stretch, lightdm is explicitly excluded by default (see Debian bug #791649), so I suggest adding it back in automatic mode.