DeleteObjects: Send delete to all pools (#172) (#20821)

Currently, DeleteObjects() tries to find the object's pool before
sending a delete request. This only works well when an object has
multiple versions in different pools since looking for the pool does
not consider the version-id. When an S3 client wants to
remove a version-id that exists in pool 2, the delete request will be
directed to pool one because it has another version of the same object.

This commit will remove looking for pool logic and will send a delete
request to all pools in parallel. This should not cause any performance
regression in most of the cases since the object will unlikely exist
in only one pool, and the performance price will be similar to
getPoolIndex() in that case.

cmd/erasure-server-pool-decom_test.go

@@ -32,9 +32,9 @@ func prepareErasurePools() (ObjectLayer, []string, error) {
 	pools := mustGetPoolEndpoints(0, fsDirs[:16]...)
 	pools = append(pools, mustGetPoolEndpoints(1, fsDirs[16:]...)...)
 
-	// Everything is fine, should return nil
-	objLayer, err := newErasureServerPools(context.Background(), pools)
+	objLayer, _, err := initObjectLayer(context.Background(), pools)
 	if err != nil {
+		removeRoots(fsDirs)
 		return nil, nil, err
 	}
 	return objLayer, fsDirs, nil