The section of the testconnection.exe you've pasted is the part that tests the deployment requirements on the target computer. The error you're seeing indicates that there was an issue remotely connecting to the task scheduler on the computer in question for the purpose of creating editing and removing tasks.
This error will not prevent successful scanning though. To successfully scan Workgroup computers, make sure the computer meets the requirements outlined here.
Alternatively, if a computer is too firewalled or you're missing the required credentials you could scan it with the LsPush scanning agent instead, which is immune to most scanning errors. For more information on LsPush and the parameters you can use you can check out this article.
