Intial sync fails when app is set to background

**Background**
Syncing the first time should download all feeds to android client that the amount of feeds equals the webinterface.

**Issue**
News-android-app does not finish its initial sync in case the app is set to background, e.g. by opening another app. Switching back to News-android-app from another app does not continue the feed download. The app simply leaves the total count of feeds incomplete.

**Expected behaviour**
The news client pauses the feed sync when another app is in foreground and continues the sync when it is active again or the news client continues syncing feeds in background.

Android app: 0.9.7
OC app: 6.0.4
OCS: 8.1.3