DAOS-16838 control: Fix dmg storage query usage with emulated NVMe

Required-githooks: true

Signed-off-by: Tom Nabarro <[email protected]>

src/control/server/instance_storage_rpc.go

@@ -460,6 +460,7 @@ func bdevScanEngineAssigned(ctx context.Context, engine Engine, req *ctlpb.ScanN
 	return scanEngineBdevsOverDrpc(ctx, engine, req)
 }
 
+// Accommodate for VMD backing devices and emulated NVMe (AIO).
 func getEffCtrlrCount(ctrlrs []*ctlpb.NvmeController) (int, error) {
 	pas := hardware.MustNewPCIAddressSet()
 	for _, c := range ctrlrs {
@@ -471,11 +472,11 @@ func getEffCtrlrCount(ctrlrs []*ctlpb.NvmeController) (int, error) {
 		if npas, err := pas.BackingToVMDAddresses(); err != nil {
 			return 0, err
 		} else {
-			pas = npas
+			return npas.Len()
 		}
 	}
 
-	return pas.Len(), nil
+	return len(ctrlrs), nil
 }
 
 // bdevScanEngine calls either in to the private engine storage provider to scan bdevs if engine process