Reduce the number of clientmgr objects created

Reduce the number of clientmgr objects created

Previously, as a way of reducing the contention between threads a
clientmgr object would be created for each interface/IP address.

We tasks being more strictly bound to netmgr workers, this is no longer
needed and we can just create clientmgr object per worker queue (ncpus).

Each clientmgr object than would have a single task and single memory
context.