Add unittests for push#2177

pmpurifoy merged 1 commit intouser/purifoypaul/PushNotificationManagerRefactormicrosoft/WindowsAppSDK:user/purifoypaul/PushNotificationManagerRefactorfrom

user/vemancha/addunittestsforpushmicrosoft/WindowsAppSDK:user/vemancha/addunittestsforpushCopy head branch name to clipboard