Only qatengine engine name allowed

looks like only:

```
ssl_engine {
use_engine qatengine;
...
}
```

is allowed. I'm building QAT Engine separately for both HW and SW paths: `qat-sw` and `qat-hw` but

```
ssl_engine {
use_engine qat-sw;
...
}
```

gives: `nginx: [emerg] invalid engine type "qat-sw" in /usr/share/nginx/conf/nginx.conf:20`