Fix early return in reaction_role_container

[dracco1993]

It looks like one of the event handlers is early returning from something, but that's not a valid thing to do in a handler. Instead, we should probably just set a flag and noop the rest of the operations or something.

Here is an example log:

020-11-06T21:38:40.462637+00:00 app[bot.1]: [ERROR : et-4914 @ 2020-11-06 21:38:40.462] Exception: #<LocalJumpError: unexpected return>
2020-11-06T21:38:40.462644+00:00 app[bot.1]: [ERROR : et-4914 @ 2020-11-06 21:38:40.462] /app/lib/bot/commands/reaction_role_container.rb:153:in `block in <class:ReactionRoleContainer>'
2020-11-06T21:38:40.462647+00:00 app[bot.1]: [ERROR : et-4914 @ 2020-11-06 21:38:40.462] /app/vendor/bundle/ruby/2.7.0/gems/discordrb-3.3.0/lib/discordrb/events/generic.rb:98:in `call'
2020-11-06T21:38:40.462682+00:00 app[bot.1]: [ERROR : et-4914 @ 2020-11-06 21:38:40.462] /app/vendor/bundle/ruby/2.7.0/gems/discordrb-3.3.0/lib/discordrb/bot.rb:1316:in `block in call_event'