Mobile: Finished hidden observation aren't shown in the past observations view

[markus-ebner]

When a hidden observation is in progress it is shown in the "current observation" view of the information tab. Once it's finished, it is not shown in "past observation".
When manually cancelling an accelerometer hidden observation, it appears under "past observations", so it seems only when it's ending automatically, it isn't shown in the "past observations".

Todo:

• Show finished hidden observation in "past observations" as well.