(PUP-2885) Remove timeout around entire plugin sync operation

This removes the timeout around the entire plugin sync. With the
default setting of configtimeout to 2min, this means that the entire
sync must be performed within this time. This conflicts with the
individual timeouts for connecting and reading and may cause that a
perfectly valid operation is timed out in the middle of productive work.
The intention is that a timeout for any individual asset being pluginsync'd will be fatal to the run, right?