VFd init script should select a CPU for VFd based on config

[ScottDaniels]

In some environments it is necessary to have the VFd init script task set the VFd process to a specific CPU even before VFd moves itself via the DPDK init function.

Proposal is to allow the desired CPU to be set in the VFd config and that it does not need to match the CPU given in the DPDK mask.