[autotest] Change devserver stats call to log data only for staging artifacts.

File names are different as they have build information included. Recording
stats for each file will create too many counters in graphite and lead to disk
space issue.

BUG=chromium:404475
TEST=local setup.
To verify metadata:
visit http://172.25.61.45:9200/_plugin/elastic-hammer/
update search url with index of local setup: dshi.mtv/_search
search for:
{
 "query": {"bool": {"minimum_should_match": 1,
                    "should": [{"term": {"_type": "devserver"}}
                              ]}},
 "size": 10000,
 "sort": [{"time_recorded": "asc"}]}

Confirm the data.

Change-Id: Ic11f76c3ef6fbf8cf5d25312d3285e1e9b87a178
Reviewed-on: https://chromium-review.googlesource.com/215640
Tested-by: Dan Shi <dshi@chromium.org>
Reviewed-by: Fang Deng <fdeng@chromium.org>
Commit-Queue: Dan Shi <dshi@chromium.org>
diff --git a/frontend/afe/model_logic.py b/frontend/afe/model_logic.py
index 6453128..ed1b2e6 100644
--- a/frontend/afe/model_logic.py
+++ b/frontend/afe/model_logic.py
@@ -713,8 +713,7 @@
         @param value: value of the state, e.g. True
         """
         metadata = {
-            'time_recorded': time.time(),
-             state: value,
+            state: value,
             'hostname': self.hostname,
         }
         es_utils.ESMetadata().post(type_str=type_str, metadata=metadata)