Enable authZ checks for member actions

Blueprint make-authz-orthogonal

This implements work item #1 of the blueprint.
This patch enables authZ checks for 'member actions' in the base
controller and removes explicit checks from l3_db.
This patch also addresses a small glitch in the policy engine which
was assuming the request always had a body.

Change-Id: I7e0f386eedcfff24ea1fee7294bbadd6c5ec781c
Merge "Enable authZ checks for member actions"