we shouldn't persist the retried failed host in db when migrating an instance

[Tao Li]

Description
===========
We set CONF.allow_resize_to_same_host to True in nova.conf. Then I migrated an instance, unfortunately nova scheduler selects the host which the instance locates in. The pre_resize will raised the UnableToMigrateToSelf exception because of the restriction of libvirt driver. Then nova scheduler will select another host to migrate, after migrating successfully, the retried host will be saved in database. From then on, the instance cann't migrate to the host any more, because the nova scheduler will check the retried hosts and bypassed them. I check the latest code, there is still this problem.

Steps to reproduce
==================
Two compute nodes and set CONF.allow_resize_to_same_host to True in nova.conf on controller node
* Create an instance
* Migrate the instance and ensure the first selected host is the host which the instance in.
* After migrate successfully, then migrate again.

Expected result
===============
The instance will migrate to the first host.

Actual result
=============
The instance migrated failed.

Environment
===========
1. Openstack Pike version.

[root@cdpm01 ~]# nova --version
9.1.1

2. libvirt driver.

Logs & Configs
==============

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/605011

[melanie witt (melwitt)]

We had a commit in the past "Don't persist RequestSpec.retry" [1] which was supposed to take care of avoiding the persist of retry information to the database. The patch was backported to Queens, Pike, and Ocata.

What version of the nova server code are you running where you see this issue? The fix is available beginning in Pike version 16.1.2.

[1] https://github.com/openstack/nova/commit/6647f11dc1aba89f9b0e2703f236a43f31d88079

[Tao Li (eric-litao)]

Hi melanie, we use version 9.1.1 of nova.

[root@cdpm05 ~]# nova --version
9.1.1

Maybe this version is old and I should banckport your commit.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Matt Riedemann (<email address hidden>) on branch: master
Review: https://review.opendev.org/605011
Reason: Already fixed with Iadbf8ec935565a6d4ccf6f36ef630ab6bf1bea5d.