Autorenewable subsciption in group cause some issue iOS

### Platform

- [x] iOS

### In-app purchase type

- [x] Auto-Renewable Subscription

### Environment

- [x] Sandbox

### Version
0.14.1

### Related issues
ℹ Please replace this with references to similar issues (either open or already closed).

## Report

### Issue summary
I have 3 products in the same group and try to use auto-renewable subscriptions with it. FIrst I subscribe to a basic product and after some time tried to subscribe standard package and both gonna subscribe.

### What did you expect to happen
I think the latest subscription should stand and all other subscriptions gonna canceled automatically.

### What happened instead
Instead, I got 2 products here in subscribe list to the same group. I don't think so this should happen.

Here is response data

kr.co.starterPackage is valid until 2019-03-09 08:06:30 +0000
DATA ---- Optional("Product Purchased")

The user has never purchased kr.co.proPackage
DATA ---- Optional("Product Not Purchased")

kr.co.standardPackage is valid until 2019-03-09 08:07:04 +0000
DATA ---- Optional("Product Purchased")

Basically, I want to know which one is active subscription right now.

No files, tests, or entry points are named in the report. Start by reproducing the three-product subscription flow in the iOS sandbox and inspect how the subscription response identifies active products; done means determining whether the duplicate active subscriptions are expected and documenting or correcting the observed behavior.

Written by the indexing model from the issue text.