Do not use absolute metrics paths.

A few places used absolute path starting with '/chrome/infra/' for
metrics reporting. This is not supported by ts_mon (at present). It
prefixes the given path with the (internal?) prefix '/chrome/infra'
irrespective of whether it is an absolute path.

So, change over to relative paths for now.

BUG=chromium:687712
TEST=None

Change-Id: I2cd1e881de8c4ea3458ebe1799337ef885fd77ff
Reviewed-on: https://chromium-review.googlesource.com/435470
Commit-Ready: Prathmesh Prabhu <pprabhu@chromium.org>
Tested-by: Prathmesh Prabhu <pprabhu@chromium.org>
Reviewed-by: Allen Li <ayatane@chromium.org>
diff --git a/server/frontend.py b/server/frontend.py
index 877cc7d..59eba6f 100644
--- a/server/frontend.py
+++ b/server/frontend.py
@@ -138,7 +138,7 @@
 
 
     @metrics.SecondsTimerDecorator(
-        '/chrome/infra/chromeos/autotest/tko/get_job_status_duration')
+            'chromeos/autotest/tko/get_job_status_duration')
     def get_job_test_statuses_from_db(self, job_id):
         """Get job test statuses from the database.