Completion of error handling about fbkutils

[jcalvinowens]

Would you like to add more error handling for return values from functions like the following?

Netconsd is Linux-specific, and none of the cases you cite can actually fail with Linux/glibc/nptl: see below. If you really want to send a pull request to fatal() if they return errors, that's fine and we'd merge it, but IMO it's not worth the trouble.

pthread_mutex_init -> create_worker_threads

See [1], this can't fail in practice: it doesn't allocate. Similarly, [2][3][4][5] show the rest can't either.

sigaction -> init_sighandlers

This one also can't fail in practice, see [6].

[1] https://code.woboq.org/userspace/glibc/nptl/pthread_mutex_init.c.html#56
[2] https://code.woboq.org/userspace/glibc/nptl/pthread_cond_init.c.html#27
[3] https://code.woboq.org/userspace/glibc/nptl/pthread_condattr_init.c.html#24
[4] https://code.woboq.org/userspace/glibc/nptl/pthread_condattr_setclock.c.html#28
[5] https://code.woboq.org/userspace/glibc/sysdeps/unix/sysv/linux/futex-internal.h.html#52
[6] https://elixir.bootlin.com/linux/v4.20-rc4/source/kernel/signal.c#L3497