xen: avoid updating node affinity twice when removing a CPU from a cpupool

93be8285 ("update domU's node-affinity on the cpupool_unassign_cpu()
path") introduced a call to domain_update_node_affinity() when a
pCPU is removed from a cpupool, but that happens already, in
cpu_disable_scheduler().

Furthermore, it causes (although only in rather awkward
circumstances), the following ASSERT to trigger:

(XEN) ****************************************
(XEN) Panic on CPU 0:
(XEN) Assertion '!cpumask_empty(dom_cpumask)' failed at domain.c:460
(XEN) ****************************************

This change, therefore, undo that.

Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
Cc: Juergen Gross <JGross@xxxxxxxx>
Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
Cc: Jan Beulich <JBeulich@xxxxxxxx>
Cc: Keir Fraser <keir.xen@xxxxxxxxx>

diff --git a/xen/common/cpupool.c b/xen/common/cpupool.c
index a758a8b..cd6aab9 100644
--- a/xen/common/cpupool.c
+++ b/xen/common/cpupool.c
@@ -379,12 +379,6 @@ static int cpupool_unassign_cpu(struct cpupool *c, unsigned int cpu)
     atomic_inc(&c->refcnt);
     cpupool_cpu_moving = c;
     cpumask_clear_cpu(cpu, c->cpu_valid);
-
-    rcu_read_lock(&domlist_read_lock);
-    for_each_domain_in_cpupool(d, c)
-        domain_update_node_affinity(d);
-    rcu_read_unlock(&domlist_read_lock);
-
     spin_unlock(&cpupool_lock);
 
     work_cpu = smp_processor_id();