Use scope instead of a query to get soft-deleted items

[Ladas]

Depends on:

• Soft delete instead of disconnect for containers models manageiq#15251

Use scope instead of a query to get soft-deleted items. The rule
of thumb should be to never do specific queries and rather
move the logic to the models.

[cben]

There is also some controllers testing deleted_on, eg.
process_show_list(:where_clause => 'container_groups.deleted_on IS NULL')
This will actually keep working without change, but let's switch that too to use scopes.

[Ladas]

@cben nice catch, yes, it's best to use 1 scope (there is also a perf impact, since deleted is indexed and deleted_on is not)

instead of
process_show_list(:where_clause => 'container_groups.deleted_on IS NULL')
we can do
process_show_list(:named_scope => :not_deleted)

[miq-bot]

Checked commits Ladas/manageiq-ui-classic@aabe976~...b1ac6cb with ruby 2.2.6, rubocop 0.47.1, and haml-lint 0.20.0
5 files checked, 0 offenses detected
Everything looks fine. 🍪

[Ladas]

@miq-bot remove_label wip, pending core

[Ladas]

@cben can you give me a last review on this? The dependency was merged

[cben]

LGTM 👍

[cben]

ping @martinpovolny this is 👍 from containers side, can someone review/merge?

@Ladas can you toggle travis, miq-syntax-checker require was fixed few days ago