clientv3: include a context in Client

Useful for clean up tasks

etcdctlv3/command/lock_command.go

@@ -46,7 +46,7 @@ func lockCommandFunc(cmd *cobra.Command, args []string) {
 }
 
 func lockUntilSignal(c *clientv3.Client, lockname string) error {
-	m := concurrency.NewMutex(context.TODO(), c, lockname)
+	m := concurrency.NewMutex(c, lockname)
 	ctx, cancel := context.WithCancel(context.TODO())
 
 	// unlock in case of ordinary shutdown