Move abstract model to katello-common package

It's being used in both Katello and Headpin mode (at least form
app/lib/notifications/notifier.rb).
Rails32 - Cleaning up TODOs from the 3.0-3.2 bridge.
katello-configure - fix script not failing when running with -b

nobars option prevented from detecting the errors in puppet script.
delayed jobs use active_record as backend

addressing:
/opt/rh/ruby193/root/usr/share/gems/gems/delayed_job-3.0.2/lib/delayed/worker.rb:75:in `before_fork': undefined method `before_fork' for nil:NilClass (NoMethodError)
        from /opt/rh/ruby193/root/usr/share/gems/gems/delayed_job-3.0.2/lib/delayed/command.rb:86:in `run_process'
        from /opt/rh/ruby193/root/usr/share/gems/gems/delayed_job-3.0.2/lib/delayed/command.rb:80:in `block in daemonize'
        from /opt/rh/ruby193/root/usr/share/gems/gems/delayed_job-3.0.2/lib/delayed/command.rb:78:in `times'
        from /opt/rh/ruby193/root/usr/share/gems/gems/delayed_job-3.0.2/lib/delayed/command.rb:78:in `daemonize'
        from script/delayed_job:5:in `<main>'
Merge pull request #1885 from iNecas/katello-configure-exit-code

katello-configure - fix script not failing when running with -b
Merge pull request #1886 from xsuchy/pull-req-jobs84

delayed jobs use active_record as backend
Merge pull request #1883 from ehelms/removing-todos

Rails32 - Cleaning up TODOs from the 3.0-3.2 bridge.
Merge pull request #1749 from iNecas/headpin-abstract-model

uninitialized constant Resources::AbstractModel::Invalid