s3: use rclone's low level retries instead of AWS SDK to fix listing retries

In 5470d34740 "backend/s3: use low-level-retries as the number
of SDK retries" we switched over to using the AWS SDK low level
retries instead of rclone's low level retry logic.

This had the unfortunate attempt that retrying listings to correct XML
Syntax errors failed on non S3 backends such as CEPH. The AWS SDK was
also retrying the XML Syntax error request which doesn't make sense.

This change turns off the AWS SDK retries in favour of just using
rclone's retry logic.

backend/s3/s3.go

@@ -1099,7 +1099,7 @@ func s3Connection(opt *Options) (*s3.S3, *session.Session, error) {
 		opt.ForcePathStyle = false
 	}
 	awsConfig := aws.NewConfig().
-		WithMaxRetries(fs.Config.LowLevelRetries).
+		WithMaxRetries(0). // Rely on rclone's retry logic
 		WithCredentials(cred).
 		WithHTTPClient(fshttp.NewClient(fs.Config)).
 		WithS3ForcePathStyle(opt.ForcePathStyle).
@@ -1206,17 +1206,12 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 		return nil, err
 	}
 
-	pc := fs.NewPacer(pacer.NewS3(pacer.MinSleep(minSleep)))
-	// Set pacer retries to 0 because we are relying on SDK retry mechanism.
-	// Setting it to 1 because in context of pacer it means 1 attempt.
-	pc.SetRetries(1)
-
 	f := &Fs{
 		name:  name,
 		opt:   *opt,
 		c:     c,
 		ses:   ses,
-		pacer: pc,
+		pacer: fs.NewPacer(pacer.NewS3(pacer.MinSleep(minSleep))),
 		cache: bucket.NewCache(),
 		srv:   fshttp.NewClient(fs.Config),
 		pools: make(map[int64]*pool.Pool),