csvimport: Merging animal duplicates is now setting location back to the default if not supplied

[bobintetley]

As title, if you make a small csv file to update a particular field in existing animal records, it's going to reset your locations and units for those animals.

This is because "internallocation" and "unit" are set from the file and can be blanks. Blanks are fine. The internallocation value is set to the default if not supplied though and this is where the problem is coming in. If we allow it to be blank for a new record, you're going to get a blank location on the resulting animal record.

It needs to set the default only if it's creating a new record. I guess we could do the dup check, then do the bit of row reading for ANIMALLOCATION and ANIMALUNIT in the new animal code path only.