Fix TestUnpadReader on Go 1.16

extern/sector-storage/fr32/readers_test.go

@@ -1,6 +1,7 @@
 package fr32_test
 
 import (
+	"bufio"
 	"bytes"
 	"io/ioutil"
 	"testing"
@@ -25,7 +26,8 @@ func TestUnpadReader(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	readered, err := ioutil.ReadAll(r)
+	// using bufio reader to make sure reads are big enough for the padreader - it can't handle small reads right now
+	readered, err := ioutil.ReadAll(bufio.NewReaderSize(r, 512))
 	if err != nil {
 		t.Fatal(err)
 	}