Bugfix: Logging does not stop when the user deactivates it

Previously, when users disabled the logging option in the settings,
the application would not stop logging and the size of the log files would increase.
Now, the option to disable it works perfectly and no logs are collected if disabled.

https://github.com/owncloud/android/pull/3436
https://github.com/owncloud/android/issues/3325
