Chunk: set disable default ( 0 )

iOSClient/Utility/CCUtility.m

@@ -693,7 +693,7 @@
     NSString *size = [UICKeyChainStore stringForKey:@"chunkSize" service:NCGlobal.shared.serviceShareKeyChain];
     
     if (size == nil) {
-        return 10;
+        return 0;
     } else {
         return [size integerValue];
     }