Fix Timeseries Query in Monitoring System Test

The old method was querying with the wrong
interval, but the test still passed because
new query objects were being unnecessarily
created, and the end time would eventually roll
over so the interval was correct. Besides being
wrong, this also led to longer back off then
necessary since results might have been available
before the rollover.

system_tests/monitoring.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import datetime
 import unittest
 
 from google.cloud.exceptions import BadRequest
@@ -201,18 +202,23 @@ def test_write_point(self):
 
         retry_500(client.write_point)(metric, resource, VALUE)
 
-        def _query_timeseries_with_retries():
-            MAX_RETRIES = 7
+        MAX_RETRIES = 7
 
-            def _has_timeseries(result):
-                return len(list(result)) > 0
+        # need to wrap built-in function for decorators to work
+        def list_timeseries(query):
+            return list(query)
 
-            retry_result = RetryResult(_has_timeseries,
-                                       max_tries=MAX_RETRIES)(client.query)
-            return RetryErrors(BadRequest, max_tries=MAX_RETRIES)(retry_result)
+        def _has_timeseries(results):
+            return len(results) > 0
+
+        endtime = datetime.datetime.utcnow()
+        query = client.query(METRIC_TYPE, end_time=endtime, minutes=5)
+
+        retry_result = RetryResult(_has_timeseries, max_tries=MAX_RETRIES)(
+            list_timeseries)
+        timeseries_list = RetryErrors(BadRequest, max_tries=MAX_RETRIES)(
+            retry_result)(query)
 
-        query = _query_timeseries_with_retries()(METRIC_TYPE, minutes=5)
-        timeseries_list = list(query)
         self.assertEqual(len(timeseries_list), 1)
         timeseries = timeseries_list[0]
         self.assertEqual(timeseries.metric, metric)