systemctl: downgrade log level of ECONNREFUSED from system dbus.service

To suppress log message when 'systemctl poweroff' or friends invoked in
rescue shell, which does not have dbus.service.

src/systemctl/systemctl-logind.c

@@ -66,7 +66,7 @@ int logind_reboot(enum action a) {
         if (!actions[a])
                 return -EINVAL;
 
-        r = acquire_bus(BUS_FULL, &bus);
+        r = acquire_bus_full(BUS_FULL, /* graceful = */ true, &bus);
         if (r < 0)
                 return r;
 
@@ -151,7 +151,7 @@ int logind_check_inhibitors(enum action a) {
         if (arg_transport != BUS_TRANSPORT_LOCAL)
                 return 0;
 
-        r = acquire_bus(BUS_FULL, &bus);
+        r = acquire_bus_full(BUS_FULL, /* graceful = */ true, &bus);
         if (r == -ECONNREFUSED && geteuid() == 0)
                 return 0; /* When D-Bus is not running, allow root to force a shutdown. E.g. when running at
                            * the emergency console. */

src/systemctl/systemctl-util.c

@@ -32,7 +32,7 @@
 
 static sd_bus *buses[_BUS_FOCUS_MAX] = {};
 
-int acquire_bus(BusFocus focus, sd_bus **ret) {
+int acquire_bus_full(BusFocus focus, bool graceful, sd_bus **ret) {
         int r;
 
         assert(focus < _BUS_FOCUS_MAX);
@@ -54,7 +54,8 @@ int acquire_bus(BusFocus focus, sd_bus **ret) {
                 else
                         r = bus_connect_transport(arg_transport, arg_host, arg_runtime_scope, &buses[focus]);
                 if (r < 0)
-                        return bus_log_connect_error(r, arg_transport, arg_runtime_scope);
+                        return bus_log_connect_full(graceful && focus == BUS_FULL && r == -ECONNREFUSED ? LOG_DEBUG : LOG_ERR,
+                                                    r, arg_transport, arg_runtime_scope);
 
                 (void) sd_bus_set_allow_interactive_authorization(buses[focus], arg_ask_password);
         }

src/systemctl/systemctl-util.h

@@ -13,7 +13,10 @@ typedef enum BusFocus {
         _BUS_FOCUS_MAX
 } BusFocus;
 
-int acquire_bus(BusFocus focus, sd_bus **ret);
+int acquire_bus_full(BusFocus focus, bool graceful, sd_bus **ret);
+static inline int acquire_bus(BusFocus focus, sd_bus **ret) {
+        return acquire_bus_full(focus, false, ret);
+}
 void release_busses(void);
 
 void ask_password_agent_open_maybe(void);