Can we do some meaningful validation of the policy?

[AltraMayor]

If so, we can test if the policy is minimally working during boot time of Grantor servers, and before updating the Lua state of Grantor servers when it's requested via the dynamic configuration block (see #142)

[AltraMayor]

Very basic check: verify that the Lua policy functions lookup_policy() and lookup_frag_punish_policy() are present. A next step is to call these function to see if they return correctly.