nas gateway: fix regression in global bucket policy initialization (#6243)

Fixes #6238
globalPolicySys used to be initialized in fs/xl layer. The referenced
commit moved this logic to server/gateway initialization,but a check
to avoid double initialization prevented globalPolicySys to be loaded
from disk for NAS.

fixes regression from commit be1700f595

cmd/gateway-main.go

@@ -217,12 +217,7 @@ func StartGateway(ctx *cli.Context, gw Gateway) {
 		logger.FatalIf(err, "Unable to initialize gateway backend")
 	}
 
-	if gw.Name() != "nas" {
-		// Initialize policy sys for all gateways. NAS gateway already
-		// initializes policy sys internally, avoid double initialization.
-		// Additionally also don't block the initialization of gateway.
 	go globalPolicySys.Init(newObject)
-	}
 
 	// Once endpoints are finalized, initialize the new object api.
 	globalObjLayerMutex.Lock()