Now returning correct experiment key without version

[aakashtiwari]

Here I am splitting key based on colon i.e. ":". If it is an experiment finished key it will be have array length greater than 2, and method will be return the key as it is. Else it will remove the version number and return the experiment name.

[andrehjr]

Thanks so much for the PR @aakashtiwari <3 Although, digging deeper into this issue I ended up fixing it on a different way with #582 without the need of changing key_without_version.

The issue was that active_experiments should not be loop on all user.keys. As you noted, the current impl of key_without_version does not work with ':finished' keys here.

Causing conflict and overriding the value of the experiment with the finished value. Which is always true.