spec: speed up spec/controllers/[a-c]*

in rails3, reduce runtime ~45% (8:10 -> 4:25 locally)

Change-Id: Ia3d17b99f1d80d5cc344ff7286244eb551a6c6b1
Reviewed-on: https://gerrit.instructure.com/38417
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Landon Wilkins <lwilkins@instructure.com>
Product-Review: Jon Jensen <jon@instructure.com>
QA-Review: Jon Jensen <jon@instructure.com>