Don't allow the `gitlab:env:info` rake task to mutate the list of omniauth providers.
Don't allow the `gitlab:env:info` rake task to mutate the list of omniauth providers.

- The test for `rake gitlab:env:info` executed the rake task, which mutated the
  list of omniauth providers, breaking subsequent tests relying on this list.

- I've changed the rake task to duplicate the providers list before modifying it.

axilleas/gitlabhq,iiet/iiet-git,dplarson/gitlabhq,dreampet/gitlab,mmkassem/gitlabhq,stoplightio/gitlabhq,jirutka/gitlabhq,iiet/iiet-git,mmkassem/gitlabhq,dreampet/gitlab,t-zuehlsdorff/gitlabhq,t-zuehlsdorff/gitlabhq,t-zuehlsdorff/gitlabhq,dplarson/gitlabhq,dplarson/gitlabhq,dreampet/gitlab,axilleas/gitlabhq,jirutka/gitlabhq,axilleas/gitlabhq,stoplightio/gitlabhq,iiet/iiet-git,t-zuehlsdorff/gitlabhq,mmkassem/gitlabhq,axilleas/gitlabhq,mmkassem/gitlabhq,dplarson/gitlabhq,jirutka/gitlabhq,stoplightio/gitlabhq,iiet/iiet-git,stoplightio/gitlabhq,dreampet/gitlab,jirutka/gitlabhq