compare_metadata does not work in case current metadata is not stored

[WenzDaniel]

We should add a fall back method which only compares the lineages in case the current data-type not stored. Currently, we are loading the metadata via:

# new metadata for the given runid + target; fetch from context
 new_metadata = self.get_metadata(run_id, target)

We should as fall back in case data is not stored:

new_lineage = st.key_for(run_id, data-type).linegae

One needs to only cast all tuples into lists or vise-versa or deactivate the type checking as otherwise one cannot compare to metadata files loaded from disk.

[WenzDaniel]

Better move to strax....