server: add test for decision log for 404.
server: add test for decision log for 404.

Signed-off-by: Xin Jin <dbb83df2f770db95cc788cf924091b643eef5483@styra.com>

open-policy-agent/opa,open-policy-agent/opa,open-policy-agent/opa,tsandall/opa,tsandall/opa,open-policy-agent/opa,tsandall/opa,open-policy-agent/opa,tsandall/opa,open-policy-agent/opa,tsandall/opa,tsandall/opa