fs: fix the defaults overriding the actual config

After re-organising the config it became apparent that there was a bug
in the config system which hadn't manifested until now.

This was the default config overriding the main config and was fixed
by noting when the defaults had actually changed.

fs/configmap.go

@@ -64,7 +64,7 @@ type regInfoValues struct {
 // the default values
 func (r *regInfoValues) Get(key string) (value string, ok bool) {
 	opt := r.options.Get(key)
-	if opt != nil && (r.useDefault || opt.Value != nil) {
+	if opt != nil && (r.useDefault || !opt.IsDefault()) {
 		return opt.String(), true
 	}
 	return "", false

fs/registry.go

@@ -244,6 +244,18 @@ func (o *Option) GetValue() interface{} {
 	return val
 }
 
+// IsDefault returns true if the value is the default value
+func (o *Option) IsDefault() bool {
+	if o.Value == nil {
+		return true
+	}
+	Default := o.Default
+	if Default == nil {
+		Default = ""
+	}
+	return reflect.DeepEqual(o.Value, Default)
+}
+
 // String turns Option into a string
 func (o *Option) String() string {
 	v := o.GetValue()