cuda: make (slow) GPUFBMemory::put/get_bytes wait for completion correctly
cuda: make (slow) GPUFBMemory::put/get_bytes wait for completion correctly

sdalton1/legion,StanfordLegion/legion,StanfordLegion/legion,sdalton1/legion,sdalton1/legion,sdalton1/legion,StanfordLegion/legion,StanfordLegion/legion,chuckatkins/legion,chuckatkins/legion,sdalton1/legion,chuckatkins/legion,sdalton1/legion,chuckatkins/legion,StanfordLegion/legion,chuckatkins/legion,chuckatkins/legion,StanfordLegion/legion,StanfordLegion/legion,chuckatkins/legion,StanfordLegion/legion