Process [compute] in $NOVA_CPU_CONF in nova-next

Due to bug 1802143, devstack was ignoring variables set in the
$NOVA_CPU_CONF section of local_conf. Now that that bug has been fixed
(see the Depends-On) we can put those back in their rightful place.

This patch moves the [compute]resource_provider_association_refresh
setting, introduced via [1], accordingly.

[1] https://review.opendev.org/616033

Depends-On: https://review.opendev.org/672805
Change-Id: Ifa50748b6d6e91ac954d0a7a6060505fd45716d4
Related-Bug: #1802143

.zuul.yaml

@@ -211,15 +211,13 @@
       tempest_black_regex: ^tempest.scenario.test_network
       devstack_local_conf:
         post-config:
-          $NOVA_CONF:
+          $NOVA_CPU_CONF:
             compute:
               # Switch off the provider association refresh, which should
               # reduce the number of placement calls in steady state. Added in
               # Stein.
-              # TODO(efried): Due to bug #1802143, nova-cpu.conf gets
-              # overwritten after post-config|$NOVA_CPU_CONF gets effected, so
-              # use $NOVA_CONF instead for now.
               resource_provider_association_refresh: 0
+          $NOVA_CONF:
             quota:
               # Added in Train.
               count_usage_from_placement: True