Add object manager interface

Add the org.freedesktop.DBus.ObjectManager interface to the root path
"/" so that InterfacesAdded signals are emitted.

The "/" path was chosen as it's the same path that the dbus-sensors
applications use for their object managers.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I842ad6affe1db780408f22a2d98160d8dddaa828
diff --git a/virtualSensor.cpp b/virtualSensor.cpp
index 5c1a6b9..e567467 100644
--- a/virtualSensor.cpp
+++ b/virtualSensor.cpp
@@ -406,6 +406,9 @@
     // Get a handle to system dbus
     auto bus = sdbusplus::bus::new_default();
 
+    // Add the ObjectManager interface
+    sdbusplus::server::manager::manager objManager(bus, "/");
+
     // Create an virtual sensors object
     phosphor::virtualSensor::VirtualSensors virtualSensors(bus);