A hack to fix opentar-42 (mail.ru ticket).

What happened in production, during upgrade:
- logger option in the config file was pointing to nowhere
- the server would start, unable to check that the child logger
process died prematurely
- the server would fork spawner process to spawn replication relays
- a replica would come in, asking for data
- the spawner would successfully spawn a relay but die on SIGPIPE
when trying to write to the log (a pipe leading nowhere by now)
about the event
-> we have a master with a dead spawner process, no more replicas,
sorry.

Well, someone should check their configuraiton in the first place.
Nevertheless, try to be nice, and:

- don't die on SIGPIPE in the spawner process.
- when starting the logger, make an effort to check that it has started
successfully. There is no reliable way to find this out, so do
it with the best effort.