Update mattermost library (#2152)

* Update mattermost library

* Fix linting

vendor/github.com/mattermost/ldap/del.go

@@ -6,9 +6,9 @@
 package ldap
 
 import (
-	"log"
-
 	ber "github.com/go-asn1-ber/asn1-ber"
+
+	"github.com/mattermost/mattermost/server/public/shared/mlog"
 )
 
 // DelRequest implements an LDAP deletion request
@@ -52,13 +52,14 @@ func (l *Conn) Del(delRequest *DelRequest) error {
 		return err
 	}
 
-	if packet.Children[1].Tag == ApplicationDelResponse {
+	tag := packet.Children[1].Tag
+	if tag == ApplicationDelResponse {
 		err := GetLDAPError(packet)
 		if err != nil {
 			return err
 		}
 	} else {
-		log.Printf("Unexpected Response: %d", packet.Children[1].Tag)
+		l.Debug.Log("Unexpected Response tag", mlog.Uint("tag", tag))
 	}
 	return nil
 }