init: fix typo and prevent startup error

metrics_library upstart job failes on boot because of a typo and soft
link command linking on existing file. Fixing the typo and add '-f' flag
when linking to supress error.

BUG=chrome-os-partner:40606
TEST=`start metrics_library`

Change-Id: I3c144f4a636a61bb460a9de74771f61ad1e6b0f9
Reviewed-on: https://chromium-review.googlesource.com/273172
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-by: Luigi Semenzato <semenzato@chromium.org>
Commit-Queue: Wei-Ning Huang <wnhuang@chromium.org>
Tested-by: Wei-Ning Huang <wnhuang@chromium.org>
diff --git a/metrics/init/metrics_library.conf b/metrics/init/metrics_library.conf
index 8202cc1..03016d1 100644
--- a/metrics/init/metrics_library.conf
+++ b/metrics/init/metrics_library.conf
@@ -15,11 +15,11 @@
   EVENTS_FILE=${METRICS_DIR}/uma-events
   mkdir -p ${METRICS_DIR}
   touch ${EVENTS_FILE}
-  chown chronos.chronos ${EVENT_FILE}
+  chown chronos.chronos ${EVENTS_FILE}
   chmod 666 ${EVENTS_FILE}
   # TRANSITION ONLY.
   # TODO(semenzato) Remove after Chrome change, see issue 447256.
   # Let Chrome read the metrics file from the old location.
   mkdir -p /var/run/metrics
-  ln -s ${EVENTS_FILE} /var/run/metrics
+  ln -sf ${EVENTS_FILE} /var/run/metrics
 end script