util: Accept TIDs for virProcess{Get,Set}Affinity() on BSD

util: Accept TIDs for virProcess{Get,Set}Affinity() on BSD

Depending on the situation, the IDs that we pass to these
functions can be either referring to processes or threads.

Linux doesn't have separate interfaces for one or the other,
but FreeBSD does and we're explicitly telling it that the ID
refers to a process. When it refers to a thread instead, the
call will fail, and the VM will not be able to start.

Luckily, another possible choice is CPU_WHICH_TIDPID, which
makes things behave the same as Linux.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>