fix(storage): retry io.ErrUnexpectedEOF (#3957)

This error can be caused by network flakiness. We already retry
it in the apiary client logic for uploads, so we should retry
here as well.

storage/go110.go

@@ -17,13 +17,17 @@
 package storage
 
 import (
+	"io"
 	"net/url"
 	"strings"
 
 	"google.golang.org/api/googleapi"
 )
 
 func shouldRetry(err error) bool {
+	if err == io.ErrUnexpectedEOF {
+		return true
+	}
 	switch e := err.(type) {
 	case *googleapi.Error:
 		// Retry on 429 and 5xx, according to

storage/go110_test.go

@@ -19,6 +19,7 @@ package storage
 import (
 	"context"
 	"errors"
+	"io"
 	"net/url"
 	"testing"
 
@@ -43,6 +44,7 @@ func TestInvoke(t *testing.T) {
 		{2, &googleapi.Error{Code: 518}, nil},
 		{2, &googleapi.Error{Code: 599}, &googleapi.Error{Code: 428}},
 		{1, &url.Error{Op: "blah", URL: "blah", Err: errors.New("connection refused")}, nil},
+		{1, io.ErrUnexpectedEOF, nil},
 	} {
 		counter := 0
 		call := func() error {