fix: totalDrives reported in speedTest for multiple-pools (#13770)

totalDrives reported in speedTest result were wrong
for multiple pools, this PR fixes this.

Bonus: add support for configurable storage-class, this
allows us to test REDUCED_REDUNDANCY to see further
maximum throughputs across the cluster.

go.mod

@@ -50,7 +50,7 @@ require (
 	github.com/minio/kes v0.14.0
 	github.com/minio/madmin-go v1.1.16
 	github.com/minio/mc v0.0.0-20211118223026-df75eed32e9e // indirect
-	github.com/minio/minio-go/v7 v7.0.16-0.20211117164632-e517704ccb36
+	github.com/minio/minio-go/v7 v7.0.16
 	github.com/minio/parquet-go v1.1.0
 	github.com/minio/pkg v1.1.9
 	github.com/minio/selfupdate v0.3.1