domain.te: Add backwards compatibility for unlabeled files

For unlabeled files, revert to DAC rules. This is for backwards
compatibility, as files created before SELinux was in place may
not be properly labeled.

Over time, the number of unlabeled files will decrease, and we can
(hopefully) remove this rule in the future.

To prevent inadvertantly introducing the "relabelto" permission, add
a neverallow domain, and add apps which have a legitimate need to
relabel to this domain.

Bug: 9777552
Change-Id: I71b0ff8abd4925432062007c45b5be85f6f70a88
diff --git a/attributes b/attributes
index 7d491e2..6123d6c 100644
--- a/attributes
+++ b/attributes
@@ -64,3 +64,6 @@
 
 # Allow domains used for platform (signed by build key) apps.
 attribute platformappdomain;
+
+# All domains which are allowed the "relabelto" permission
+attribute relabeltodomain;