btl/ugni: fix race condition in completing frags#5372

jsquyres merged 1 commit intoopen-mpi:v3.1.xopen-mpi/ompi:v3.1.xfrom

hjelmn:v3.1.x_btl_ugni_racehjelmn/ompi:v3.1.x_btl_ugni_raceCopy head branch name to clipboard