No, definitely attach it to the back of the pot.

You'd be better off attaching the shield wire directly to the pot, even if it means having to de-solder the signal wire, shorten it a bit and re-soldering. Looking at the photo I'd recommend that you do it anyway, as that exposed shield wire could easily move and touch one of the signal wires and short it out. Unless you have any heat-shrink insulation handy, I'd cut the shield really short so that as it leaves the overall cable insulation it is soldered directly to the back of the volume pot, and have a longer length of the inner signal wire that then goes to the volume pot lug.

Note that it will be lead-free solder that the factory used, so use lead-free to re-solder it. Leaded and lead-free don't mix well (or so I've been told).