OAK-1247: Non-deterministic access control test failures

Make PermissionValidator get the PermissionProvider from the before state
instead of from the commit info. This makes the permission checks more
deterministic and avoids the problem of commits from an unrefreshed
session being potentially evaluated against outdated permission settings.

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1552356 13f79535-47bb-0310-9956-ffa450edef68