Convert mac address to lower case always

Without this commit there is a possible bug if the user
request a mac address with upper case.

The issue is that netlink lib will always return the hardware struct
for mac address and it will always be lower case.

So to be able and do a right equal check we convert the user provided mac
address to lower case always

Signed-off-by: Sebastian Sch <sebassch@gmail.com>

cmd/sriov/main.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"runtime"
+	"strings"
 
 	"github.com/containernetworking/cni/pkg/skel"
 	"github.com/containernetworking/cni/pkg/types"
@@ -66,6 +67,9 @@ func cmdAdd(args *skel.CmdArgs) error {
 		netConf.MAC = netConf.RuntimeConfig.Mac
 	}
 
+	// Always use lower case for mac address
+	netConf.MAC = strings.ToLower(netConf.MAC)
+
 	netns, err := ns.GetNS(args.Netns)
 	if err != nil {
 		return fmt.Errorf("failed to open netns %q: %v", netns, err)