Fix duplicate DOM IDs and broken flash messages in miq_ae_class_controller

[martinpovolny]

• flash message related IDs are duplicate
• class_fields_div is nesting (messed up update and replace)
• form_group and form_div are used many times

Fixes:
https://bugzilla.redhat.com/show_bug.cgi?id=1405178

[martinpovolny]

@h-kataria : please, review

[miq-bot]

Checked commits martinpovolny/manageiq-ui-classic@2a206bb~...3ba2746 with ruby 2.2.6, rubocop 0.47.1, and haml-lint 0.20.0
3 files checked, 0 offenses detected
Everything looks good. 🍰

[h-kataria]

looks good, verified fix in UI.

[simaishi]

@martinpovolny 5 out of 6 files are conflicting... Please resolve conflict and create an Euwe-specific PR (referencing this one) or suggest other PRs to backport.

$ git status
On branch euwe
Your branch is up-to-date with 'origin/euwe'.
You are currently cherry-picking commit e809b39.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:

	modified:   app/views/miq_ae_class/_all_tabs.html.haml

Unmerged paths:
  (use "git add <file>..." to mark resolution)

	both modified:   app/controllers/miq_ae_class_controller.rb
	both modified:   app/views/miq_ae_class/_class_fields.html.haml
	both modified:   app/views/miq_ae_class/_class_instances.html.haml
	both modified:   app/views/miq_ae_class/_class_methods.html.haml
	both modified:   app/views/miq_ae_class/_class_props.html.haml

[simaishi]

Changed to euwe/no as per ManageIQ/manageiq#15125 (comment)