Fix unused linter warnings

Fix the following warnings:

export_test.go:12:31: func `lowerCaseExport.foo` is unused (unused)
func (export lowerCaseExport) foo() (string, *Error) {
                              ^
conn.go:935:29: func `(*callTracker).finalize` is unused (unused)
func (tracker *callTracker) finalize(sn uint32) {
                            ^
variant_parser.go:420:2: field `val` is unused (unused)
	val      interface{}
	^
default_handler.go:218:25: func `(*exportedObj).isFallbackInterface` is unused (unused)
func (obj *exportedObj) isFallbackInterface() bool {
                        ^
variant_parser.go:577:2: field `val` is unused (unused)
	val        interface{}
	^

Signed-off-by: Kir Kolyshkin <[email protected]>

conn.go

@@ -941,17 +941,6 @@ func (tracker *callTracker) handleSendError(msg *Message, err error) {
 	}
 }
 
-// finalize was the only func that did not strobe Done
-func (tracker *callTracker) finalize(sn uint32) {
-	tracker.lck.Lock()
-	defer tracker.lck.Unlock()
-	c, ok := tracker.calls[sn]
-	if ok {
-		delete(tracker.calls, sn)
-		c.ContextCancel()
-	}
-}
-
 func (tracker *callTracker) finalizeWithBody(sn uint32, sequence Sequence, body []interface{}) {
 	tracker.lck.Lock()
 	c, ok := tracker.calls[sn]

default_handler.go

@@ -215,10 +215,6 @@ func (obj *exportedObj) LookupMethod(name string) (Method, bool) {
 	return nil, false
 }
 
-func (obj *exportedObj) isFallbackInterface() bool {
-	return false
-}
-
 func newExportedIntf(methods map[string]Method, includeSubtree bool) *exportedIntf {
 	return &exportedIntf{
 		methods:        methods,

export_test.go

@@ -9,10 +9,6 @@ import (
 
 type lowerCaseExport struct{}
 
-func (export lowerCaseExport) foo() (string, *Error) {
-	return "bar", nil
-}
-
 type fooExport struct {
 	message Message
 }

variant_parser.go

@@ -417,7 +417,6 @@ func (b boolNode) Value(sig Signature) (interface{}, error) {
 type arrayNode struct {
 	set      sigSet
 	children []varNode
-	val      interface{}
 }
 
 func (n arrayNode) Infer() (Signature, error) {
@@ -574,7 +573,6 @@ type dictEntry struct {
 type dictNode struct {
 	kset, vset sigSet
 	children   []dictEntry
-	val        interface{}
 }
 
 func (n dictNode) Infer() (Signature, error) {