When removing one of the network elements a wrong one got removed

Description

When trying to remove one of 2 Network Elements not the one with the chosen UUID got removed but another one. This happened when using the CLI with mongoDB. (Maybe this also happens with other store modes, or when sending requests with sth else then the CLI. Needs some investigation here.)

Expected Behavior

The Network Element with the chosen UUID gets removed from storage.

Actual Behavior

Any other MNE got removed.

Steps to Reproduce

1. Start controller with mongoDB.
2. Add 2 Network Elements.
3. Remove one of the elements.