Langjian/allreduce provenance tag (#3120)
Langjian/allreduce provenance tag (#3120)

* Print provenance_tag name for allreduce op

* Fix a bug

* remove friendly_name print out

* Fix

* More debug

* More bugs

* Bug

* More meaningful outputs

* Better output

* c_str()

* Print friendly_name or provenance_tags

* Print provenance_tags when available

* Add comments

* style

NervanaSystems/ngraph,NervanaSystems/ngraph,NervanaSystems/ngraph,NervanaSystems/ngraph