chore: let db_conn_or_core_shutdown and init_apm_or_core_shutdown reraise their exceptions

[viniarck]

Once PR #414 lands, there's room to simplify both db_conn_or_core_shutdown and init_apm_or_core_shutdown and allow their exceptions to be caught as a broad one, during controller.start, since we're already dealing with a broad exc for this case anyway to catch any sort of error, so it should be ok without compromising redability, this is just a chore, functionality wise it'll behave the same:

https://github.com/kytos-ng/kytos/blob/master/kytos/core/controller.py#L254-L258