BadUserAccessDenied: when reconnecting to the service using the opcua-simulator

**During reconnection, this function `encryptPasswords(userIds)` should not be executed multiple times.**

 `ioTSensorsOPCUA/services/uaSrvService.go`

```
...
server.WithAuthenticateUserNameIdentityFunc(func(
        encryptPasswords(userIds)
...
```

**fix**: like this

```
var once sync.Once
...
once.Do(func() {
        encryptPasswords(userIds)
})
```