Make default executor Graph method not completely error out when
encountering an unparseable yaml file.

Signed-off-by: Fredrik Lönnegren <fredrik.lonnegren@suse.com>

In this commit we add back the error when trying to load a corrupt yaml
file, but we still execute the entire graph first, making the command
fail with an error about which path failed to load, but not breaking the
execution for other yaml files.

Signed-off-by: Fredrik Lönnegren <fredrik.lonnegren@suse.com>