spec: speed up more slow model specs

reduce runtime of modified specs by >40% (9:05 -> 5:20)

Change-Id: I42f2aaaf92b4ea5c0a2c476b1e66dbe068de1961
Reviewed-on: https://gerrit.instructure.com/38488
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>