Nix 2.0 no longer uses these directories.
/run/nix/current-load was moved to /nix/var/nix/current-load in 2017
(Nix commit d7653dfc6dea076ecbe00520c6137977e0fced35). Anyway,
src/build-remote/build-remote.cc will create the current-load directory
if it doesn't exist already.
/run/nix/remote-stores seems to have been deprecated since 2014 (Nix
commit b1af336132cfe8a6e4c54912cc512f8c28d4ebf3) when the documentation
for $NIX_OTHER_STORES was removed, and support for it was dropped
entirely in 2016 (Nix commit 4494000e04122f24558e1436e66d20d89028b4bd).
dab5c632bd