Initialize global object layer after all subsystems have initialized (#6333)

This is to ensure that object API operations are not performed
on a server on which subsystems are yet to be initialized.

cmd/policy.go

@@ -77,10 +77,6 @@ func (sys *PolicySys) Remove(bucketName string) {
 
 // IsAllowed - checks given policy args is allowed to continue the Rest API.
 func (sys *PolicySys) IsAllowed(args policy.Args) bool {
-	if sys == nil {
-		return args.IsOwner
-	}
-
 	sys.RLock()
 	defer sys.RUnlock()