possibly confusing warning from standalone controller for custom authkeys

If you provide a custom application.conf with your own user entry, you get a warning like this:

```
[ WARN ] Configure wsk via below command to connect to this server as [guest]

wsk property set --apihost 'http://localhost:3233' --auth '23bc46b1-71f6-4ed5-8c54-816aa4f8c502:123zO3xZCLrMN6v2BKK1dXYFpXlPkccOFqm12CdAsMgRU4VrNZ9lyGVCGuMDGIwP'
[ OK ] Server port [3233] is free
```

This is because in my case the host was not configured correctly. The `auth` string in this case is the built-in guest key and not the one I specified. This could be confusing for some users but I'm not sure how to fix it so opening the issue for discussion/ideas.

Reproduce the standalone controller warning with a custom application.conf containing a user entry, then follow how the warning and the wsk property set command obtain the displayed auth key. Done means the warning no longer presents the built-in guest key when a custom key or host configuration is in use, with the expected behavior covered by a suitable test.

Written by the indexing model from the issue text.