Greatly reduce test duration for git_access_spec
Greatly reduce test duration for git_access_spec

- Combine multiple `it` blocks into one where it made sense
- Use `set` for the top-level User record
- Refactor permission matrix tests

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