Use label staging_data_file for installed APEX.

This is needed in cases SELinux labels are restored under /data/apex by
an external process calling restorecon. In normal condition files under
/data/apex/active retain the label staging_data_file used at their
original creation by StagingManager. However, we observed that the label
might be changed to apex_data_file, which we were able to reproduce by
running restorecon.

Explicitly mark files under /data/apex/active and /data/apex/backup as
staging_data_file.

This CL also remove some stale rules being addressed since.

Test: ran restorecon on files in /data/apex/active, attempted installing
a new apex which triggered the violation when files are linked to
/data/apex/backup. With this CL, the operation succeeds.
Bug: 112669193
Change-Id: Ib4136e9b9f4993a5b7e02aade8f5c5e300a7793c
diff --git a/private/file_contexts b/private/file_contexts
index 83be009..39244c1 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -434,6 +434,8 @@
 /data/adb(/.*)?		u:object_r:adb_data_file:s0
 /data/anr(/.*)?		u:object_r:anr_data_file:s0
 /data/apex(/.*)?		u:object_r:apex_data_file:s0
+/data/apex/active/(.*)?		u:object_r:staging_data_file:s0
+/data/apex/backup/(.*)?		u:object_r:staging_data_file:s0
 /data/app(/.*)?                       u:object_r:apk_data_file:s0
 /data/app/[^/]+/oat(/.*)?                u:object_r:dalvikcache_data_file:s0
 /data/app/vmdl[^/]+\.tmp(/.*)?           u:object_r:apk_tmp_file:s0