use ancestry in replace_children

[d-m-u]

the api uses replace_children (https://github.com/ManageIQ/manageiq-api/blob/01bb977042d6b75e73a0e568b4b3fd455b9d0ec7/app/controllers/api/vms_controller.rb#L107) which, as it isn't an ancestry method, wasn't extended to use the gem functionality.

currently broken: any api call that's updating vm ancestry

thanks @agrare
this fixes the failing api specs

@miq-bot assign @agrare
@miq-bot add_label bug

broken in #20274

related: ManageIQ/manageiq-api#994

[d-m-u]

rspec ./spec/requests/vms_spec.rb:364 # Vms API Vm edit can edit a VM with an appropriate role has two failing expectations:

     1.3) Failure/Error: expect(vm.reload.children).to match_array(new_vms)

            expected collection contained:  [#<ManageIQ::Providers::Openstack::CloudManager::Vm id: 71000000000124, vendor: "openstack", format: ...emory_hot_add_increment: nil, hostname: nil, ems_ref_type: nil, restart_needed: nil, ancestry: nil>]
            actual collection contained:    [#<ManageIQ::Providers::Openstack::CloudManager::Vm id: 71000000000122, vendor: "openstack", format: ..._increment: nil, hostname: nil, ems_ref_type: nil, restart_needed: nil, ancestry: "71000000000121">]
            the missing elements were:      [#<ManageIQ::Providers::Openstack::CloudManager::Vm id: 71000000000124, vendor: "openstack", format: ...emory_hot_add_increment: nil, hostname: nil, ems_ref_type: nil, restart_needed: nil, ancestry: nil>]
            the extra elements were:        [#<ManageIQ::Providers::Openstack::CloudManager::Vm id: 71000000000122, vendor: "openstack", format: ..._increment: nil, hostname: nil, ems_ref_type: nil, restart_needed: nil, ancestry: "71000000000121">]
          # ./spec/requests/vms_spec.rb:389:in `block (3 levels) in <top (required)>'
          # /Users/drewmu/.rvm/gems/ruby-2.5.5/gems/webmock-3.11.1/lib/webmock/rspec.rb:37:in `block (2 levels) in <top (required)>'

should be fixed by the replace_children addition here

     1.4) Failure/Error: expect(vm.parent).to eq(vm_openstack2)

            expected: #<ManageIQ::Providers::Openstack::CloudManager::Vm id: 71000000000126, vendor: "openstack", format: n...memory_hot_add_increment: nil, hostname: nil, ems_ref_type: nil, restart_needed: nil, ancestry: nil>
                 got: nil

should be fixed by the save!, which i think is the responsibility of the caller, so the accompanying pr adds that single line

[agrare]

LGTM, @kbrock can you eyeball this as well?

[miq-bot]

Checked commit d-m-u@fb77dbf with ruby 2.6.3, rubocop 0.82.0, haml-lint 0.35.0, and yamllint
2 files checked, 0 offenses detected
Everything looks fine. 🏆