Do not pass our disk cache path up to NSURLCache.

diff --git a/SDURLCache b/SDURLCache
index 894a1b139f21e85e28a235bb97b1654923ce3d72..ad6d6aca4ddadeec7dfa65f5f1c24344c3c01f5e 160000 (submodule)
--- a/SDURLCache
+++ b/SDURLCache
@@ -1 +1 @@
-Subproject commit 894a1b139f21e85e28a235bb97b1654923ce3d72
+Subproject commit ad6d6aca4ddadeec7dfa65f5f1c24344c3c01f5e