AU: move AU completed marker from /tmp to /var/run since /var/run is root-only.

BUG=6578
TEST=unit tests, gmerged on device, updated, restarted update engine and
checked status

Change-Id: If703b66f1bf6efa13f25225d3c5868bc3dd190b7

Review URL: http://codereview.chromium.org/3404015
diff --git a/update_attempter.cc b/update_attempter.cc
index a1568a9..73b93b8 100644
--- a/update_attempter.cc
+++ b/update_attempter.cc
@@ -36,7 +36,8 @@
 
 namespace chromeos_update_engine {
 
-const char* kUpdateCompletedMarker = "/tmp/update_engine_autoupdate_completed";
+const char* kUpdateCompletedMarker =
+    "/var/run/update_engine_autoupdate_completed";
 
 const char* UpdateStatusToString(UpdateStatus status) {
   switch (status) {