NotificationServices.remoteNotifications contains two elements instead of one, when a notification is received through APNs.

Steps to reproduce:
1) Set up an App ID for use with push notifications.
2) Create and save a certificate in the Keychain via Apple Developer site.
3) Open the attached project.
4) Build for iOS.
5) Open the project and make sure the 'Push Notifications' field is enabled in the Capabilities tab.
6) Run on a device.
7) Copy the array of numbers/letters that appears in the console (device token).
8) Stop the app via Xcode.
9) Open Pusher (attached in project folder).
10) Select the certificate you created earlier from the drop-down.
11) Paste the device token.
12) Press 'Push'.
13) When a notification appears, tap on it to re-open the app.

NotificationServices.remoteNotifications.Length is logged in the top-left. Even though one notification was sent, 2 is returned on the screen.

Reproduced on:
5.6.0b6, 5.4.4p2, 5.3.7p3

Did not reproduce:
5.2.4f1

Devices tested:
iPhone 7 iOS 10.3
iPhone 5 iOS 9.3.5
iPhone 5S iOS 9.3.3

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Fix was backported to 5.6, 5.5 & 5.4