README: use /run paths
README: use /run paths

Since /var/run is a symlink to /run, and we want to avoid going
through the stateful /var whenever possible, use the direct path.

BUG=chromium:699880
TEST=precq passes

Change-Id: I5d95f5358c1fb0cb2ca73f9c4b145d8e36b4a361
Reviewed-on: https://chromium-review.googlesource.com/734225
Commit-Ready: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Reviewed-by: Zach Reizner <3374927928a53d04457674c546bd4de57c2044ec@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm