Make spec tests use Grack::Auth in a way consistent with the rails route (!1904) · Merge requests · GitLab.org / GitLab FOSS

Following 30bf2b9c the rails route uses Grack::AuthSpawner instead of Grack::Auth directly. Do the same in spec tests.

This will be especially useful for gitlab-org/gitlab-ee!29

NB: I did not feel a CHANGELOG entry was appropriate for this, but please let me know if I should add one nevertheless.

Make spec tests use Grack::Auth in a way consistent with the rails route