Use service_registry_path() in create_exit_action().

As a result of registry function refactoring we were constructing the
default path to AppExit incorrectly.  Using the function created for the
purpose works correctly, unsurprisingly.

Thanks Igor Zenkov.

registry.cpp

@@ -189,7 +189,7 @@ int create_parameters(nssm_service_t *service, bool editing) {
 int create_exit_action(TCHAR *service_name, const TCHAR *action_string, bool editing) {
   /* Get registry */
   TCHAR registry[KEY_LENGTH];
-  if (_sntprintf_s(registry, _countof(registry), _TRUNCATE, NSSM_REGISTRY _T("\\%s"), service_name, NSSM_REG_EXIT) < 0) {
+  if (service_registry_path(service_name, true, NSSM_REG_EXIT, registry, _countof(registry)) < 0) {
     log_event(EVENTLOG_ERROR_TYPE, NSSM_EVENT_OUT_OF_MEMORY, _T("NSSM_REG_EXIT"), _T("create_exit_action()"), 0);
     return 1;
   }