[#493] node/config: Always read the values of ENV variables

In previous implementation ENV values were read only if config filepath is
specified. From now ENVs are always read to `Config`.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

cmd/neofs-node/config/config.go

@@ -36,15 +36,16 @@ type Prm struct{}
 func New(_ Prm, opts ...Option) *Config {
 	v := viper.New()
 
+	v.SetEnvPrefix(EnvPrefix)
+	v.AutomaticEnv()
+	v.SetEnvKeyReplacer(strings.NewReplacer(separator, EnvSeparator))
+
 	o := defaultOpts()
 	for i := range opts {
 		opts[i](o)
 	}
 
 	if o.path != "" {
-		v.SetEnvPrefix(envPrefix)
-		v.AutomaticEnv()
-		v.SetEnvKeyReplacer(strings.NewReplacer(separator, envSeparator))
 		v.SetConfigFile(o.path)
 
 		err := v.ReadInConfig()