StorageScan button spec - fix spec after .ext_management_systems removal

[himdel]

.ext_management_systems was removed from Storage in ManageIQ/manageiq#19754
fixing the specs to use .ext_management_system (singular).

Cc @kbrock

Fixes red travis:

  1) ApplicationHelper::Button::StorageScan when feature is supported #calculate_properties with valid credentials for this Datastore behaves like an enabled button is expected to be truthy
     Failure/Error: expect(subject[:enabled]).to be_truthy

       expected: truthy value
            got: false
     Shared Example Group: "an enabled button" called from ./spec/helpers/application_helper/buttons/storage_scan_spec.rb:35
     # ./spec/support/examples_group/shared_examples_for_enabled_buttons.rb:4:in `block (2 levels) in <top (required)>'
  2) ApplicationHelper::Button::StorageScan when feature is supported #calculate_properties but no EMS has valid credentials for the Datastore behaves like a disabled button is expected to eq "There are no EMSs with valid credentials for this Datastore"
     Failure/Error: expect(subject[:title]).to eq(err_msg)

       expected: "There are no EMSs with valid credentials for this Datastore"
            got: "Smartstate Analysis cannot be performed on selected Datastore"

       (compared using ==)
     Shared Example Group: "a disabled button" called from ./spec/helpers/application_helper/buttons/storage_scan_spec.rb:32
     # ./spec/support/examples_group/shared_examples_for_disabled_buttons.rb:5:in `block (2 levels) in <top (required)>'

rspec ./spec/helpers/application_helper/buttons/storage_scan_spec.rb:35 # ApplicationHelper::Button::StorageScan when feature is supported #calculate_properties with valid credentials for this Datastore behaves like an enabled button is expected to be truthy
rspec ./spec/helpers/application_helper/buttons/storage_scan_spec.rb:32 # ApplicationHelper::Button::StorageScan when feature is supported #calculate_properties but no EMS has valid credentials for the Datastore behaves like a disabled button is expected to eq "There are no EMSs with valid credentials for this Datastore"

[agrare]

@himdel could you create the storage record in this context with the ems instead of stubbing the call? Now that it is a simple belongs to that is a lot easier to do where before you'd have to link it up to hosts and host storages.

[himdel]

sure, updated :)

[miq-bot]

Checked commits https://github.com/himdel/manageiq-ui-classic/compare/0675c7dd8cc76ee78c5fe8795f0093fb0a60d2aa~...aeebaf1003bb6c85107a63e5e4830f202a0516d6 with ruby 2.5.5, rubocop 0.69.0, haml-lint 0.20.0, and yamllint 1.10.0
1 file checked, 0 offenses detected
Everything looks fine. ⭐

[kbrock]

Thanks. Looking good