Panic on start when BindAddr cannot be resolved

[buraksezer]

Olric panics on start if BindAddr is invalid or cannot be resolved. It should return an error and quit with exit code 1.

Sample config:

olricd:
  # BindAddr denotes the address that Olric will bind to for communication
  # with other Olric nodes.
  bindAddr: foobar

➜  olric git:(release/v0.5.0) ✗ olricd -c cmd/olricd/olricd-local.yaml
2023/02/01 20:13:24 [INFO] pid: 2055 has been started
2023/02/01 20:13:24 [ERROR] Failed to start Olric: invalid BindAddr: lookup foobar: no such host
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x78 pc=0x10477b6c8]

goroutine 1 [running]:
github.com/buraksezer/olric.(*Olric).Shutdown(0x0, {0x1049b7bd8, 0x140000eddc0})
	/Users/buraksezer/go/src/github.com/buraksezer/olric/olric.go:397 +0x28
github.com/buraksezer/olric/cmd/olricd/server.(*Olricd).Shutdown(...)
	/Users/buraksezer/go/src/github.com/buraksezer/olric/cmd/olricd/server/server.go:101
main.main()
	/Users/buraksezer/go/src/github.com/buraksezer/olric/cmd/olricd/main.go:128 +0x54c