split property context file in vendor and sytem were left untouched by
the recent changes. This was working accidentally because they were
still accessible to all domains as 'system_file'.

Bug: 36002573
Test: Boot sailfish to observe no new denials.
Test: 'adb sideload' OTA on sailfish successfully

Change-Id: I5bec058b59db83d2a431e9f7e91c5a09af7d2942
Signed-off-by: Sandeep Patil <sspatil@google.com>