Changes from [[post-config|$NOVA_CPU_CONF]] are overwritten in "superconductor" mode

[Matt Riedemann]

Noticed here:

https://review.openstack.org/#/c/616033/1

That is setting a post-config for the nova-cpu.conf here:

          [[post-config|$NOVA_CPU_CONF]]
          [compute]
          resource_provider_association_refresh = 0

Which gets set in devstack initially:

http://logs.openstack.org/33/616033/1/check/nova-next/6e893b8/logs/devstacklog.txt.gz#_2018-11-07_00_24_44_044

2018-11-07 00:24:44.047 | ++ inc/meta-config:merge_config_file:164 : iniset /etc/nova/nova-cpu.conf compute resource_provider_association_refresh 0

But later overwritten when nova.conf is copied to nova-cpu.conf:

http://logs.openstack.org/33/616033/1/check/nova-next/6e893b8/logs/devstacklog.txt.gz#_2018-11-07_00_26_29_702

2018-11-07 00:26:29.695 | + lib/nova:start_nova_compute:897 : local compute_cell_conf=/etc/nova/nova.conf
2018-11-07 00:26:29.698 | + lib/nova:start_nova_compute:900 : [[ superconductor == \s\i\n\g\l\e\c\o\n\d\u\c\t\o\r ]]
2018-11-07 00:26:29.702 | + lib/nova:start_nova_compute:907 : cp /etc/nova/nova.conf /etc/nova/nova-cpu.conf

The workaround is to put nova-cpu.conf configuration in $NOVA_CONF but it's confusing and we should merge the nova-cpu.conf rather than overwrite it.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/672805

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/672805
Committed: https://git.openstack.org/cgit/openstack/devstack/commit/?id=2468ceaa724aa5c8c44fb87ae223eb6687ff85f2
Submitter: Zuul
Branch: master

commit 2468ceaa724aa5c8c44fb87ae223eb6687ff85f2
Author: Eric Fried <email address hidden>
Date: Thu Jul 25 13:18:58 2019 -0500

    Merge (don't overwrite) $NOVA_CPU_CONF

    Per the referenced bug, $NOVA_CPU_CONF was previously being initialized
    by copying $NOVA_CONF, thereby trashing any values already configured in
    $NOVA_CPU_CONF.

    With this commit, we merge the values from $NOVA_CPU_CONF in after the
    copy.

    Note that this makes use of the merge_config_file function, which is
    defined in inc/meta-config, which wasn't being sourced from every code
    path that hit start_nova_compute; so this commit also moves that import
    from stack.sh to functions (next to the other imports from inc/, which
    makes sense anyway).

    Change-Id: Id3e2baa2221e13f512f8dcf1248e1e15b6a7597f
    Closes-Bug: #1802143