Bug#845180: some "target" need to be replaced by dereferenced_target in app/models/repository.rb

[张敬强]

According to code in 
https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/models/repository.rb

, I changed ".target" and ":target" to dereferenced_target,

then the "Branches" Page work again, and branch deletion also work again.



Thanks