summarizer: better handling of local yaml files
When reading a packager-provided yaml module file, some optional
information like module name, module stream or module defaults can be
missing. These are usually filled out by the module build service from
the module's git repo. So to correctly handle local yamls, we cannot use
the same modulemd_index_from_file call for both local and repo yamls.
See https://github.com/fedora-modularity/libmodulemd/issues/125
Signed-off-by: Rafael dos Santos <rdossant@redhat.com>