fix: make sure to use uniform drive count calculation (#10208)

It is possible in situations when server was deployed
in asymmetric configuration in the past such as

```
minio server ~/fs{1...4}/disk{1...5}
```

Results in setDriveCount of 10 in older releases
but with fairly recent releases we have moved to
having server affinity which means that a set drive
count ascertained from above config will be now '4'

While the object layer make sure that we honor
`format.json` the storageClass configuration however
was by mistake was using the global value obtained
by heuristics. Which leads to prematurely using
lower parity without being requested by the an
administrator.

This PR fixes this behavior.

cmd/config-current.go

@@ -213,7 +213,7 @@ var (
 	globalServerConfigMu sync.RWMutex
 )
 
-func validateConfig(s config.Config) error {
+func validateConfig(s config.Config, setDriveCount int) error {
 	// Disable merging env values with config for validation.
 	env.SetEnvOff()
 
@@ -233,8 +233,7 @@ func validateConfig(s config.Config) error {
 	}
 
 	if globalIsErasure {
-		if _, err := storageclass.LookupConfig(s[config.StorageClassSubSys][config.Default],
-			globalErasureSetDriveCount); err != nil {
+		if _, err := storageclass.LookupConfig(s[config.StorageClassSubSys][config.Default], setDriveCount); err != nil {
 			return err
 		}
 	}
@@ -311,7 +310,7 @@ func validateConfig(s config.Config) error {
 		globalNotificationSys.ConfiguredTargetIDs())
 }
 
-func lookupConfigs(s config.Config) {
+func lookupConfigs(s config.Config, setDriveCount int) {
 	ctx := GlobalContext
 
 	var err error
@@ -382,8 +381,7 @@ func lookupConfigs(s config.Config) {
 	globalAPIConfig.init(apiConfig)
 
 	if globalIsErasure {
-		globalStorageClass, err = storageclass.LookupConfig(s[config.StorageClassSubSys][config.Default],
-			globalErasureSetDriveCount)
+		globalStorageClass, err = storageclass.LookupConfig(s[config.StorageClassSubSys][config.Default], setDriveCount)
 		if err != nil {
 			logger.LogIf(ctx, fmt.Errorf("Unable to initialize storage class config: %w", err))
 		}
@@ -601,7 +599,7 @@ func loadConfig(objAPI ObjectLayer) error {
 	}
 
 	// Override any values from ENVs.
-	lookupConfigs(srvCfg)
+	lookupConfigs(srvCfg, objAPI.SetDriveCount())
 
 	// hold the mutex lock before a new config is assigned.
 	globalServerConfigMu.Lock()