Update rename_system_namespace_spec to new validations.
Update rename_system_namespace_spec to new validations.

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