Update rust-installer to fix rust-lang-nursery/rustup.rs#1092

diff --git a/src/rust-installer b/src/rust-installer
index 4cf7397fb0566e745f0bce4c5b009cfeb5d12c53..2e6417f6af5218a29a8ee72ed17af085560b9b9c 160000 (submodule)
--- a/src/rust-installer
+++ b/src/rust-installer
@@ -1 +1 @@
-Subproject commit 4cf7397fb0566e745f0bce4c5b009cfeb5d12c53
+Subproject commit 2e6417f6af5218a29a8ee72ed17af085560b9b9c