Update db.get_did()

[ershockley]

With updates to strax(en) plugins there are now data entries with multiple DIDs for the same run _+ datatype. Need to update db.get_did to account for this.

For example:

>>> db.get_did(8005, 'peaklets')
'xnt_008005:peaklets-nagx3zzuiv'

But there is actually a more up-to-date hash ioudwhzz4n:

>>> data = db.get_data(8005)
>>> for d in data:
...     if d['type'] == 'peaklets':
...             print(d.get('did'))
...
None
xnt_008005:peaklets-nagx3zzuiv
xnt_008005:peaklets-ioudwhzz4n