Add a method for closing the dbus system bus connection

If the dbus system bus connection is marked as private, then
allow it to be closed.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

src/libvirt_private.syms

@@ -1102,6 +1102,7 @@ virConfWriteMem;
 
 # util/virdbus.h
 virDBusCallMethod;
+virDBusCloseSystemBus;
 virDBusGetSessionBus;
 virDBusGetSystemBus;
 virDBusHasSystemBus;

src/util/virdbus.c

@@ -122,6 +122,14 @@ virDBusHasSystemBus(void)
 }
 
 
+void virDBusCloseSystemBus(void)
+{
+    if (systembus && !sharedBus) {
+        dbus_connection_close(systembus);
+        systembus = NULL;
+    }
+}
+
 static void virDBusSessionBusInit(void)
 {
     sessionbus = virDBusBusInit(DBUS_BUS_SESSION, &sessiondbuserr);
@@ -1310,6 +1318,10 @@ virDBusHasSystemBus(void)
     return false;
 }
 
+void virDBusCloseSystemBus(void)
+{
+    /* nothing */
+}
 
 DBusConnection *virDBusGetSessionBus(void)
 {

src/util/virdbus.h

@@ -35,6 +35,7 @@ void virDBusSetSharedBus(bool shared);
 
 DBusConnection *virDBusGetSystemBus(void);
 bool virDBusHasSystemBus(void);
+void virDBusCloseSystemBus(void);
 DBusConnection *virDBusGetSessionBus(void);
 
 int virDBusCallMethod(DBusConnection *conn,