check_send_receive_time: Default --site usefully.

This saves us the time of shelling out to a new python process,
loading all of Django, and printing one value we could just have read
in-process.  It is unclear why we ever did it this way.

puppet/kandra/manifests/prod_app_frontend_once.pp

@@ -21,7 +21,7 @@ class kandra::prod_app_frontend_once {
   zulip::cron { 'check_send_receive_time':
     hour      => '*',
     minute    => '*',
-    command   => '/usr/lib/nagios/plugins/zulip_app_frontend/check_send_receive_time --site=https://$(/home/zulip/deployments/current/scripts/get-django-setting NAGIOS_BOT_HOST)',
+    command   => '/usr/lib/nagios/plugins/zulip_app_frontend/check_send_receive_time',
     use_proxy => false,
   }
   zulip::cron { 'check_user_zephyr_mirror_liveness':

puppet/kandra/manifests/profile/staging_app_frontend.pp

@@ -22,7 +22,7 @@ class kandra::profile::staging_app_frontend inherits kandra::profile::base {
   zulip::cron { 'check_send_receive_time':
     hour      => '*',
     minute    => '*',
-    command   => '/usr/lib/nagios/plugins/zulip_app_frontend/check_send_receive_time --site=https://$(/home/zulip/deployments/current/scripts/get-django-setting NAGIOS_BOT_HOST)',
+    command   => '/usr/lib/nagios/plugins/zulip_app_frontend/check_send_receive_time',
     use_proxy => false,
   }
 }

puppet/zulip/files/nagios_plugins/zulip_app_frontend/check_send_receive_time

@@ -24,18 +24,6 @@ setup_path()
 import django
 import zulip
 
-usage = """Usage: send-receive.py [options] [config]
-
-       'config' is optional, if present will return config info.
-        Otherwise, returns the output data."""
-
-parser = argparse.ArgumentParser(usage=usage)
-parser.add_argument("--site", default="https://api.zulip.com")
-
-parser.add_argument("--insecure", action="store_true")
-
-options = parser.parse_args()
-
 sys.path.append("/home/zulip/deployments/current")
 os.environ["DJANGO_SETTINGS_MODULE"] = "zproject.settings"
 
@@ -46,6 +34,17 @@ from django.conf import settings
 from zerver.models.realms import get_realm
 from zerver.models.users import get_system_bot
 
+usage = """Usage: send-receive.py [options] [config]
+
+       'config' is optional, if present will return config info.
+        Otherwise, returns the output data."""
+
+parser = argparse.ArgumentParser(usage=usage)
+parser.add_argument("--site", default=f"https://{settings.NAGIOS_BOT_HOST}")
+parser.add_argument("--insecure", action="store_true")
+
+options = parser.parse_args()
+
 states = {
     "OK": 0,
     "WARNING": 1,