Speed up Project security access specs

Merged Robert Speicher requested to merge rs-project-security-spec-speed-ee into master

Prior, every single test was creating four ProjectMember objects, each of which created one User record, even though each test only used one of those Users, if any.

Now each test only creates the single user record it needs, if it needs one. This shaves minutes off of each spec file changed here.

EE version of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7779