Use shared callMethod function in control manager

To better handle exit/restart of the fan control application use the
shared callMethod function to call systemd's startunit on the fan
control ready target. This allows the fan control application to exit
and restart quickly in its allowed attempts configured in systemd.

Tested:
    StartUnit on fan control ready target works the same

Change-Id: Idce2d8831b4e8de0ef181a0849587e465419f68c
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
diff --git a/control/manager.cpp b/control/manager.cpp
index a322c10..1078473 100644
--- a/control/manager.cpp
+++ b/control/manager.cpp
@@ -122,26 +122,14 @@
         delay = sleep(delay);
     }
 
-    startFanControlReadyTarget();
-}
-
-
-void Manager::startFanControlReadyTarget()
-{
-    auto method = _bus.new_method_call(SYSTEMD_SERVICE,
-                                       SYSTEMD_OBJ_PATH,
-                                       SYSTEMD_INTERFACE,
-                                       "StartUnit");
-
-    method.append(FAN_CONTROL_READY_TARGET);
-    method.append("replace");
-
-    auto response = _bus.call(method);
-    if (response.is_method_error())
-    {
-        log<level::ERR>("Failed to start fan control ready target");
-        elog<InternalFailure>();
-    }
+    util::SDBusPlus::callMethod(
+            _bus,
+            SYSTEMD_SERVICE,
+            SYSTEMD_OBJ_PATH,
+            SYSTEMD_INTERFACE,
+            "StartUnit",
+            FAN_CONTROL_READY_TARGET,
+            "replace");
 }
 
 } // namespace control