Feature Request: Interpret zypper --recommends properly in Dockerfile builds

[Werkov]

Container builds in OBS with Dockerfile don't run with the same repositories as if the commands were run manually. OBS parses the Dockerfile internaly and creates a temporary repo with preloaded build deps.
An understandable default for container images is solver.onlyRequires=false, however, some packages may be desired with zypper in --recommends.

OBS should preload the recommended deps (transitive closure) and let the zypper running inside container during build decide the resolution (subset of the closure may be installed).