Fix Remove Selected Items from Inventory button for Images, Instances

[hstastna]

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1601955

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There is a problem with 'Remove selected items from Inventory' button in all the pages under Compute > Clouds while trying to remove Instance or Image. It's because validate_destroy method is called every time we try to delete some item but this method is available only for Host, at least for now.

Steps to reproduce: (one of possible scenarios)

1. Go to Compute > Clouds > Providers and add some provider if there is no one
2. In provider's details screen, in Relationships table, click on Images/Instances
3. Choose some Images/Instances (check the checkboxes)
4. Click on Configuration > Remove selected items from Inventory
   => the selected Images/Instances are not removed, error:

I, [2018-07-19T11:06:07.102659 #9372]  INFO -- : Started POST "/ems_cloud/button/38?pressed=image_delete" for ::1 at 2018-07-19 11:06:07 +0200
I, [2018-07-19T11:06:07.152445 #9372]  INFO -- : Processing by EmsCloudController#button as JS
I, [2018-07-19T11:06:07.153491 #9372]  INFO -- :   Parameters: {"miq_grid_checks"=>"2099", "check_2099"=>"2099", "pressed"=>"image_delete", "id"=>"38"}
F, [2018-07-19T11:06:07.382083 #9372] FATAL -- : Error caught: [NoMethodError] undefined method `validate_destroy' for #<ManageIQ::Providers::Amazon::CloudManager::Template:0x007f803d597d28>
Did you mean?  validate_stop
/home/hstastna/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/activemodel-5.0.7/lib/active_model/attribute_methods.rb:433:in `method_missing'
/home/hstastna/manageiq/manageiq/app/models/mixins/availability_mixin.rb:24:in `is_available?'

Before:

After:

[hstastna]

@miq-bot add_label bug, blocker, gaprindashvili/yes

[miq-bot]

Checked commit hstastna@7de8cf2 with ruby 2.3.3, rubocop 0.52.1, haml-lint 0.20.0, and yamllint 1.10.0
2 files checked, 0 offenses detected
Everything looks fine. ⭐

[hstastna]

@Ladas What do you think about that? Thank you ;)

[Ladas]

Looks good 👍

[Ladas]

@agrare the story here is the the "Remove from VMDB" button never had any check, but UI guys are consolidating the buttons code, so now every action needs to have .supports?

[Ladas]

@miq-bot assign @agrare

[agrare]

👍 good find, I wonder how many other buttons are like this though 😱

[simaishi]

As per BZ Target Release, removing gaprindashvili/yes