Add policy checking for transfer create/accept.

This patch adds policy checks for transfer create/accept
as well as adding the associated default policy.  In addition
we add the wrap in the volume/api accept_transfer method.

Fixes bug: 1187910

Change-Id: I599ac0a95cea1605380d4595a1f21023fbcfb6f1
Merge "Add policy checking for transfer create/accept."