[BUGFIX] Properly expand parent roles in Policy.yaml core migration
The core migration ``TYPO3.Flow-20141113121400`` that rewrites existing
``Policy.yaml`` files to match the reworked Security Framework also
adjusted the role identifiers that were allowed to only contain the
role name without package key prefix if used in the current package.
With this fix the role identifier expansion now also works for
referenced parent roles.
Releases: master, 3.0