Use rugged.references.delete to delete reference
Use rugged.references.delete to delete reference

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7237#note_19746468

openwide-java/gitlabhq,openwide-java/gitlabhq,axilleas/gitlabhq,openwide-java/gitlabhq,t-zuehlsdorff/gitlabhq,iiet/iiet-git,dreampet/gitlab,dreampet/gitlab,iiet/iiet-git,t-zuehlsdorff/gitlabhq,dplarson/gitlabhq,t-zuehlsdorff/gitlabhq,dreampet/gitlab,stoplightio/gitlabhq,dplarson/gitlabhq,jirutka/gitlabhq,LUMC/gitlabhq,openwide-java/gitlabhq,jirutka/gitlabhq,mmkassem/gitlabhq,dplarson/gitlabhq,axilleas/gitlabhq,LUMC/gitlabhq,dplarson/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,htve/GitlabForChinese,darkrasid/gitlabhq,axilleas/gitlabhq,stoplightio/gitlabhq,LUMC/gitlabhq,dreampet/gitlab,iiet/iiet-git,axilleas/gitlabhq,jirutka/gitlabhq,htve/GitlabForChinese,jirutka/gitlabhq,darkrasid/gitlabhq,LUMC/gitlabhq,htve/GitlabForChinese,mmkassem/gitlabhq,mmkassem/gitlabhq,htve/GitlabForChinese,iiet/iiet-git,darkrasid/gitlabhq,t-zuehlsdorff/gitlabhq,darkrasid/gitlabhq,stoplightio/gitlabhq