When the nova-compute service starts, by default it attempts to
startup instance configuration states for aspects such as networking.
This is fine in most cases, and makes a lot of sense if the
nova-compute service is just managing virtual machines on a hypervisor.
This is done, one instance at a time.
However, when the compute driver is ironic, the networking is managed
as part of the physical machine lifecycle potentially all the way into
committed switch configurations. As such, there is no need to attempt
to call ``plug_vifs`` on every single instance managed by the
nova-compute process which is backed by Ironic.
Additionally, using ironic tends to manage far more physical machines
per nova-compute service instance then when when operating co-installed
with a hypervisor. Often this means a cluster of a thousand machines,
with three controllers, will see thousands of un-needed API calls upon
service start, which elongates the entire process and negatively
impacts operations.
In essence, nova.virt.ironic's plug_vifs call now does nothing,
and merely issues a debug LOG entry when called.
Closes-Bug: #1777608
Change-Id: Iba87cef50238c5b02ab313f2311b826081d5b4ab
(cherry picked from commit 7f81cf28bf21ad2afa98accfde3087c83b8e269b)
(cherry picked from commit eb6d70f02daa14920a2522e5c734a3775ea2ea7c)