Trap SignalExceptions in Job.reserve

Delayed Job [handles trapping the signals and acting upon the signal](https://github.com/collectiveidea/delayed_job/blob/v4.0.0/lib/delayed/worker.rb#L135-L145), but we get raised the `SignalException` due to our setting of `Delayed::Worker.raise_signal_exceptions` to true. And then let that bubble out to the error handler.

Instead, now log that we saw a `SignalException`, but don't let it bubble out of `TomQueue::DelayedJob::Job.reserve`.