Shared parts can be detected by presence of .shared file or presence of any
shared_part_list paths in .installed.cfg, and in such case do not allow to
upload to binary cache.

It's better than checking presence of shared_part_list in the configuration,
as this does not give real information if the shared technique was using
during installing given release.

This adapts 19e3f1b6 to 5cbd70bc