Raise bad request when current_group is specified on edit

[jntullo]

Editing of a current_group is allowed only on on the set_current_group action.

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1549086

[miq-bot]

Checked commit jntullo@d2e8ea4 with ruby 2.3.3, rubocop 0.52.0, haml-lint 0.20.0, and yamllint 1.10.0
2 files checked, 0 offenses detected
Everything looks fine. 🍰

[abellotti]

LGTM !! we don't allow current_group_id, so this is the reference signature equivalent. 👍

[simaishi]

Fine backport (to manageiq repo) details:

$ git log -1
commit 8460d9b01422a1cbed0b933a1f1da76fbfb9731c
Author: Alberto Bellotti <abellotti@users.noreply.github.com>
Date:   Tue Feb 27 09:29:01 2018 -0500

    Merge pull request #329 from jntullo/bz_1549086
    
    Raise bad request when current_group is specified on edit
    (cherry picked from commit 40cf625ebcbf56b9df316196463bbc6c011aaf92)
    
    Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1551693

[simaishi]

@jntullo Travis is failing in Fine branch, can you please address?

1) users API users edit does not allow edits of current_user
     Failure/Error: "href"          => api_user_url(nil, user1),
     NoMethodError:
       undefined method `api_user_url' for #<RSpec::ExampleGroups::UsersAPI::UsersEdit:0x000000313317c0>
     # /home/travis/.rvm/gems/ruby-2.3.1/gems/actionpack-5.0.6/lib/action_dispatch/testing/assertions/routing.rb:175:in `method_missing'
     # /home/travis/.rvm/gems/ruby-2.3.1/gems/actionpack-5.0.6/lib/action_dispatch/testing/integration.rb:491:in `method_missing'
     # ./spec/requests/api/users_spec.rb:196:in `block (3 levels) in <top (required)>'

[jntullo]

@simaishi would you like me to create a fine-specific PR for this entire backport? or should I just create a fine-specific PR to fix just this failure? (it's a small fix)

[simaishi]

Since this PR is already backported to Fine branch, please create a PR just to fix the failure. Thank you!

[simaishi]

Gaprindashvili backport details:

$ git log -1
commit 7f0cf0fbb32b5aef2ac8c41ab54082767f373344
Author: Alberto Bellotti <abellotti@users.noreply.github.com>
Date:   Tue Feb 27 09:29:01 2018 -0500

    Merge pull request #329 from jntullo/bz_1549086
    
    Raise bad request when current_group is specified on edit
    (cherry picked from commit 40cf625ebcbf56b9df316196463bbc6c011aaf92)
    
    Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1551692