mstask: Implemented DllUnregisterServer.

dlls/mstask/mstask.spec

@@ -25,3 +25,4 @@
 @ stub _SASetNSAccountInformation@12
 @ stub _SetNetScheduleAccountInformation@12
 @ stdcall -private DllRegisterServer()
+@ stdcall -private DllUnregisterServer()

dlls/mstask/mstask_main.c

@@ -155,3 +155,8 @@ HRESULT WINAPI DllRegisterServer(void)
 {
     return register_mstask(TRUE);
 }
+
+HRESULT WINAPI DllUnregisterServer(void)
+{
+    return register_mstask(FALSE);
+}