Hi,
securelogin.arubanetworks.com is a self signed certificate and you will always get cert error. This is unavoidable.
The way to get pass it, is to install a public certificate which your browser (client devices) trust such as verisign, comodo etc. If public cert is not possible, you can proceed with private cert but in this case, you will need to install the root certificate of CA on every client device (which may or may not be feasible).
So to be concise and clear, the only fool proof method to avoid cert error is to use public cert.