Reenables true multithreaded s3 copy (#2423)
Reenables true multithreaded s3 copy (#2423)

Boto3 update removed multithreaded file copy in favor of multithreaded multipart file copy.
PeteW/luigi,riga/luigi,spotify/luigi,adaitche/luigi,Magnetic/luigi,adaitche/luigi,foursquare/luigi,rayrrr/luigi,soxofaan/luigi,dlstadther/luigi,soxofaan/luigi,dlstadther/luigi,foursquare/luigi,Magnetic/luigi,jamesmcm/luigi,spotify/luigi,rayrrr/luigi,Magnetic/luigi,riga/luigi,jamesmcm/luigi,jamesmcm/luigi,soxofaan/luigi,PeteW/luigi,samuell/luigi,samuell/luigi,rayrrr/luigi,foursquare/luigi,adaitche/luigi,PeteW/luigi,spotify/luigi,riga/luigi,jamesmcm/luigi,PeteW/luigi,rayrrr/luigi,dlstadther/luigi,riga/luigi,spotify/luigi,adaitche/luigi,samuell/luigi,dlstadther/luigi,samuell/luigi,soxofaan/luigi,foursquare/luigi,Magnetic/luigi