* add mpirun support for openmpi 4.0

* add master addr support from args

* switch mpi detection to use mpi4py

* set constant for default distributed port

* Make sure deepspeed_mpi exits in args

* add auto-detect to torch dist init

* update tests to infer distributed init status

* prevent crash if dist_init_required is True but already initiliazed

* only init if safe to do so (forgot to add this file in prev commit)

* Support legacy optimizer fusion as config option

* Configure for legacy optimizer fusion

* Update configuration jsons for new apex

Also a fix for #94