fix: keep decommission in a go-routine (#17496)

This was removed by mistake in #17491

cmd/erasure-server-pool-decom.go

@@ -1114,11 +1114,13 @@ func (z *erasureServerPools) Decommission(ctx context.Context, indices ...int) e
 		return err
 	}
 
-	for _, idx := range indices {
-		// decommission all pools serially one after
-		// the other.
-		z.doDecommissionInRoutine(ctx, idx)
-	}
+	go func() {
+		for _, idx := range indices {
+			// decommission all pools serially one after
+			// the other.
+			z.doDecommissionInRoutine(ctx, idx)
+		}
+	}()
 
 	// Successfully started decommissioning.
 	return nil