I need to establish some clarity regarding your question - first, when you say ginger grass, do you mean Paspalum distichum, common name ginger grass, or do you mean Zingiber officinale, the knobbly root grown for culinary/medicinal use, which also produces grass like leaves on top? I'm assuming you mean the latter, in which case, this plant grows in Zones 10 or 11 outdoors for a few months - once the leaves die back, the root is harvested. You appear to reside in Zone 5, so you won't be able to grow this outdoors other than possibly during summer.
I'm also not sure what you mean by 'will it keep the grass at bay', but as you can't grow it outdoors at this time of year anyway, its probably now irrelevant. If, though, you were asking whether growing ginger would keep other grass from encroaching on your rhubarb, no, it wouldn't, you need to remove the grass by weeding it out yourself.