First of all because it's not needed that early, and second of all
because there's a bug where calling `sway --get-socketpath` via `popen`
causes the child sway process to spin/hang instead of returning EOF.
(Specifically `(unset SWAYSOCK; swaymsg)` hangs.) This patch fixes that.
(Also note that this patch moves the "detailed review" comment, so I
guess this patch requires extra detailed review?)