dcsindex: skip files whose name is not valid UTF-8
dcsindex: skip files whose name is not valid UTF-8

This is to prevent breakage later on in the system. Such files cause the
JSON response from the index-backend to be (entirely!) invalid, so we
just don’t index the files at all.

jamessan/dcs,jamessan/dcs,lamby/dcs,jamessan/dcs,lamby/dcs,jamessan/dcs,lamby/dcs,lamby/dcs