credential store is getting duplicates, need to be better at handling this

[taquitos]

When we add the git user credentials to the local store, we need to make sure we are not duplicating them, and that we actually remove them when done.
We also need to be careful we don't remove them when another build is using them.

mini:~ jliebowitz$ cat .gitconfig | grep "helper = store --file" |wc -l
**219**

[fastlane-danger-bot]

We decided to pause our work on fastlane.ci to focus on the core fastlane product as we have a lot on the roadmap. You can find more information on the main GitHub page. This issue will be auto-closed 👍