Fix realtime upload times

The last fix for this didn't work because clean_fields() made database
calls to verify the datasource field. This fix saves objects
individually when the bulk_create fails.
For future reference, @notthatbreezy, the total number of records has no bearing on the ideal batch insert size.  Benchmarking is needed to determine that; generally 1,000 records is cited as being a good size to start with.  I ask here because I was curious if some benchmarking was done.