Change end date in test_update_host_reservation

This patch changes the end date of leases to update in a test scenario
to have a period of time to prevent them from being rejected with the
"End date must be later than current and start date" error.

Change-Id: Id8bc8d5c850dd10d2d85b51620b2effe5494320e
Closes-Bug: #1821731

blazar_tempest_plugin/tests/scenario/test_host_reservation.py

@@ -294,7 +294,7 @@ class TestHostReservationScenario(rrs.ResourceReservationScenarioTest):
         time.sleep(75)
 
         # update the lease end_time
-        end_time = datetime.datetime.utcnow()
+        end_time = datetime.datetime.utcnow() + datetime.timedelta(seconds=30)
         body = {
             'end_date': end_time.strftime('%Y-%m-%d %H:%M')
             }