strange behavior on Updating a file

### Actual behaviour
I opened a file stored on the server (**not** marked to be offline available in the Details... of the APP). It was a OpenOffice Spreadsheet. The file get's downloaded and is opened with AndrOpenOffice.

After changing and saving the spreadsheet. The file does **not** get uploaded by nextcloud-APP.
There was no information in the Upload-activity-log.

After that I checked the box **_offline available_**. In the same moment the file get's uploaded to the server.

### Expected behaviour
depends on the design spec:
I assume that a file not to be stored locally (offline available = false) is copied to the tmp folder and opened from there. If this file is updated and the server file is to be updated by specification I expect the file to be immediately updated on the server (or at least within seconds). If an update of the file in the tmp folder will not be updated on the server by design then I would not expect the file to be uploaded after marking the file **_offline available_**

### Steps to reproduce
1. Create a spreadsheet file with openoffice on the PC and wait until it is uploaded to the server
2. open the file by tipping it in nextcloudAPP
3. change it and save it
4. wait some minutes to check whether the file is going to be uploaded (in my case it is not uploaded)
5. now long-tip on the file in nextCloudApp, select ... Menu - Details, check the **_offline available_** checkbox - the modified file immediately get's uploaded to the server

### Environment data
Android version:
6.0.1

Device model:
Google Nexus 5

Stock or customized system:
stock

Nextcloud app version:
20161129-beta

Nextcloud server version:
10.0.1

regards

Peter