Revert "Increases delta of start_time when collecting OpenStack metrics"

This reverts commit 1b6b0e02f6f82ccc8a441e26bb42183f63a48acc.

Change-Id: Ieabe8e515fb3cfb5aa96802e4c5bc1305c21f2b3
diff --git a/osm_mon/collector/collectors/openstack.py b/osm_mon/collector/collectors/openstack.py
index 30bab0c..395d607 100644
--- a/osm_mon/collector/collectors/openstack.py
+++ b/osm_mon/collector/collectors/openstack.py
@@ -99,8 +99,7 @@
                 for param in vdu['monitoring-param']:
                     metric_name = param['nfvi-metric']
                     gnocchi_metric_name = METRIC_MAPPINGS[metric_name]
-                    delta = 10 * self.granularity
-                    start_date = datetime.datetime.now() - datetime.timedelta(seconds=delta)
+                    start_date = datetime.datetime.now() - datetime.timedelta(seconds=self.granularity)
                     resource_id = self._get_resource_uuid(nsr_id, vnf_member_index, vdur['name'])
                     try:
                         measures = self.gnocchi_client.metric.get_measures(gnocchi_metric_name,