Allow overwriting of values

[HoboDev]

Is your feature request related to a problem? Please describe.
Mentioned in issue #82
The problem is that overwriting a value does not sync properly (but it should).
This might be more an issue of charm kv.

Describe the solution you'd like
set a new value for an existing key and have it sync properly.

Describe alternatives you've considered
Deleting the key/value pair and setting it again works. But it's not charming.