Recursively restorecon when SELinux label changes.

PackageManager has been pretty aggressive about asking installd to
restorecon over app data when it thinks something might have
changed.  However, in the vast majority of cases these are no-op
requests, and we waste a bunch of time recursively walking all
private data, easily costing 60+ seconds on dogfooder devices.

This change relies on new installd "create_app_data" behavior that
kicks off a recursive restorecon if it detects that the top-level
SELinux label on the app private data directory changes.  This means
that PackageManager no longer needs to track restoreconNeeded state.

Test: booted, verified that a label change triggered restorecon
Bug: 30768146
Change-Id: I0c8d4018cf8ff888d0ae07a82adc3d61a6002aad