Implement a mechanism for permissible file repair

Implement a mechanism for permissible file repair

Permissible files that have been marked as invalid due to their hash
not matching can now be repaired by fetching the relevant data directly
form PrivilegeDb. This works for both the service and the client library.
As the client lacks the privileges to do it on their own, in that case
a request is sent to the Security Manager daemon.

Change-Id: I43fee3d39c015a7fbba0e674c29c904ac26e91bf