fix(sshd): unlock the repository when gitreceive succeeds or fails

[kmala]

Summary of Changes

Currently the builder is not unlocking the repo if the git push succeeds or fails because of which we can't do multiple releases to any app

Issue(s) that this PR Closes

Associated End To End Test PR(s)

Associated Documentation PR(s)

Associated Design Document(s)

Testing Instructions

Please provide a detailed list for how to test the changes in this PR.

1. Create a Deis Cluster
2. Register an app
3. do git push again or do a new release and you should succeed.

   Pull Request Hygiene TODOs

Please make sure the below checklist is complete.

• [x] Your pull request is concise and to the point (make another PR for refactoring nearby code)
• [x] Your commits follow the commit style guidelines

[deis-bot]

@smothiki, @aledbf and @arschles are potential reviewers of this pull request based on my analysis of git blame information. Thanks @kmala!

[arschles]

LGTM3