Warnings about s3aio

[Kirill888]

When calling dc.load for the first time warnings are printed "Failed to resolve driver datacube.plugins.io.read::s3aio"

import datacube.drivers.readers
datacube.drivers.readers.reader_drivers()

Error is due to missing sharedarray dependency in the s3 drivers or something, but really datacube should not be installed with s3 option.