v2.4.0

Features

• add data parallelism support (#11) (#12)

Bug Fixes and Other Changes

• use ubuntu 18.04 base image in dlc gpu image
• remove TODOs in 1.6.0 dlc gpu dockerfile and reduce parameters for data parallel integ test
• use base cuda 11 image for test dlc gpu image
• use 1.6.0 for gpu tests and disable horovod tests
• remove local data parallel integ test
• use sagemaker-training 3.7.0 and enable data parallel integ tests
• patch socket call and update flake8 violations