kvmtool: Set the thread names for terminal and virtio-net-ctrl

The terminal handling thread and the virtio-net-ctrl don't
set their name, which ends up as follows up:

 terminal => lkvm
 virtio-net-ctrl => kvm-cpu-X !!

Set the thread name explicitly to term-poll and virtio-net-ctrl
respectively

Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>