libxl: automatically set soft affinity after vnuma info

libxl: automatically set soft affinity after vnuma info

More specifically, vcpus are assigned to a vnode, which in
turn is associated with a pnode. If a vcpu does not have any
soft affinity, automatically build up one, matching the pcpus
of the said pnode.

Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Ian Jackson <Ian.Jackson@eu.citrix.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>