Don't know if MH370 even had fire bottles such as the one pictured, because of the phasing out of Halon systems. The Maldives are quite far from the present search area. I'd be surprised if the Inmarsat calculations were that far off. I think the engineers have done a great job helping to narrow down a search area. Plus, wouldn't other things have washed up around the same area if this bottle was from a recent crash?
Replacing Halon in Fire Protection Systems: A Progress Report