blacklisted event names in settings.yml

[durandom]

default blacklisted event names are now sourced from settings.yml

this allows providers just provide a setting in

 :ems:
   :ems_<%= provider_name %>:
     :blacklisted_event_names: []

I moved the method to BaseManager, because I think it belongs there and BaseManager has the provider inflection methods (to get the provider name via provider_name)

In a follow up PR, we can remove the method in the subclasses and just add the events to settings.yml in the provider repo.

ps. I just realised there is ExtManagementSystem.short_token, which arguably could also be used. I'll replace this method later with the inflection methods.

cc @agrare @bronaghs @blomquisg

@Fryguy please review

[durandom]

@miq-bot assign @Fryguy
@miq-bot add_labels enhancement, pluggable providers

[miq-bot]

Checked commits durandom/manageiq@2c24c3a~...7b2bd75 with ruby 2.2.6, rubocop 0.47.1, and haml-lint 0.20.0
3 files checked, 0 offenses detected
Everything looks good. 🏆

[agrare]

This looks great, we can get rid of the hard-coded default events while still allowing new blacklisted events to be added per provider-type or per provider by adding them to the db.

[durandom]

@Fryguy is this good to go?