Replace correct usage for the netlink default

This use case of the literal is correct, and calls out the reason for
explicitly setting TxQLen. This change switches to the helper still.

plugins/main/bridge/bridge.go

@@ -335,16 +335,11 @@ func bridgeByName(name string) (*netlink.Bridge, error) {
 }
 
 func ensureBridge(brName string, mtu int, promiscMode, vlanFiltering bool) (*netlink.Bridge, error) {
+	linkAttrs := netlink.NewLinkAttrs()
+	linkAttrs.Name = brName
+	linkAttrs.MTU = mtu
 	br := &netlink.Bridge{
-		LinkAttrs: netlink.LinkAttrs{
-			Name: brName,
-			MTU:  mtu,
-			// Let kernel use default txqueuelen; leaving it unset
-			// means 0, and a zero-length TX queue messes up FIFO
-			// traffic shapers which use TX queue length as the
-			// default packet limit
-			TxQLen: -1,
-		},
+		LinkAttrs: linkAttrs,
 	}
 	if vlanFiltering {
 		br.VlanFiltering = &vlanFiltering