LANDesk does not have official antivirus support for server platforms yet, though I think LANDesk plans on it. 8.7 was really the first release of AV and LANDesk wanted to get very very very stable before moving it to the server platform. We had some very large issues in the early stages that caused instability. This instability has cleared up little by little over time. Now, as of SP4 we are pretty stable so I would expect us to start moving to the server platform soon.
So to answer your question, you cannot install it by default using the Server Agent Configuration. I don't know yet about 8.8, but this is 8.7 answer. I don't think it has changed in 8.8.
I have heard that some customer have manually added AV by doing an advanced edit on the Server Agent Configuration.
Server Manager doesn't integrate with the server manager client. If you want to install LDMS AV on your servers you will need to use the regular client and not the Server Manager client.
Doh, I was punked. To slow in my response.
Thanks. This really makes sense to me.