When getting all monitors set parameter "with_downtimes" to true

Change in Datadog api requires this parameter to correctly report
if monitor is silenced

dogpush/dogpush.py

@@ -139,12 +139,13 @@ def _canonical_monitor(original, default_team=None, **kwargs):
 
 
 def get_datadog_monitors():
-    monitors = datadog.api.Monitor.get_all()
+    monitors = datadog.api.Monitor.get_all(with_downtimes="true")
     if CONFIG['dogpush']['ignore_prefix'] is not None:
         monitors = [
             m for m in monitors
             if not m['name'].startswith(CONFIG['dogpush']['ignore_prefix'])
         ]
+
     if not _check_monitor_names_unique(monitors):
         raise DogPushException(
             'Duplicate names found in remote datadog monitors.')