Rename context names of zram properties

Moving from old bad name "exported*_prop".

Bug: 154885206
Bug: 155844385
Test: m selinux_policy
Change-Id: I21af42980e5e6e2c3cabea6c36825fa2836a55bc
diff --git a/private/property.te b/private/property.te
index 7591b85..ca9f2ca 100644
--- a/private/property.te
+++ b/private/property.te
@@ -345,3 +345,9 @@
 } {
   libc_debug_prop
 }:property_service set;
+
+neverallow {
+  -init
+  -system_server
+  -vendor_init
+} zram_control_prop:property_service set;