The above command will perform a silent installation and run the ONTAP AV Connector service as the specified service account(at least, it worked on my test machine). I probably wouldn't pass plaintext passwords to the installer, but your scripting langauge of choice will likely have a way to store credential strings securely.
Re: Installing Antivirus connector in silent/unattended mode
The "Configure ONTAP Management LIFs for Polling" shortcut is actually a different program called mregfa.exe, so we can't pass arguments to it from the MSI installer (or not easily, anyways).
However, once you launch the program and put in your appropriate LIF, poll interval, and account settings, you can click on the "Export" button and it'll dump a .reg file to a location of your choosing, which makes it super easy to configure the AV Connector programatically on other machines - just import the .reg file into the registery and away you go!