Remove superfluous context.path

It was generating URLs that look like
http://server.example.com/gitbucket/gitbucket/git/user/repo.git (notice
the extra "/gitbucket"?) when the WAR was deployed in Tomcat.
Resolves error when deleting repsository with PR.
Merge pull request #202 from odz/delete-repository-with-pullreq

Resolves Error when deleting repository which has PR.
Merge pull request #203 from olivierdagenais/FixManualMergeUrls

Remove superfluous context.path