spec: improve brand_config_controller coverage
spec: improve brand_config_controller coverage

closes CNVS-33721

test plan: specs should pass, coverage should improve

Change-Id: Ia8065b1ffc8f941ef0665f40ebfbbaa406399162
Reviewed-on: https://gerrit.instructure.com/96980
Tested-by: Jenkins
Reviewed-by: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>
Product-Review: Simon Williams <088e16a1019277b15d58faf0541e11910eb756f6@instructure.com>
QA-Review: Simon Williams <088e16a1019277b15d58faf0541e11910eb756f6@instructure.com>

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