Remove SERVICE_X_BUTTON_ALLOWED_ACTIONS

[mzazrivec]

No longer needed since 63f214f

[miq-bot]

Checked commit mzazrivec@e0e2e11 with ruby 2.3.3, rubocop 0.47.1, haml-lint 0.20.0, and yamllint 1.10.0
2 files checked, 0 offenses detected
Everything looks fine. 👍

[martinpovolny]

Something is wrong here (not in this PR, but before).

I don't see why @hstastna remove the x_button in 63f214f

There should have never been both x_button and button.

I see that before that @lgalis was chaning both of these so there's some history to this strangeness.

Overall this seems broken to me I don't see how all the methods from the hash are called now.

[martinpovolny]

Note: #2680 was already backported to Gaprindashvili.

[martinpovolny]

63f214f also breaks generic objects

the line

+    action = @sb[:action] if action.nil?                                                           

causes action being set even when it should not be set and then

        if action                                                                                   
          cb_tb = build_toolbar(Mixins::CustomButtons::Result.new(:single))                         
          r[:partial => partial, :locals => {:item_id => @item.id}]     

gets called

the newly added code is very fragile and hard to read, @lgalis