Add selinux rules for userspace reboot related properties

By default sys.init.userspace_reboot.* properties are internal to
/system partition. Only exception is
sys.init.userspace_reboot.in_progress which signals to all native
services (including vendor ones) that userspace reboot is happening,
hence it should be a system_public_prop.

Only init should be allowed to set userspace reboot related properties.

Bug: 135984674
Test: builds
Test: adb reboot userspace
Change-Id: Ibb04965be2d5bf6e81b34569aaaa1014ff61e0d3
diff --git a/private/property_contexts b/private/property_contexts
index 16c8d93..ff79c34 100644
--- a/private/property_contexts
+++ b/private/property_contexts
@@ -22,6 +22,7 @@
 hw.                     u:object_r:system_prop:s0
 ro.hw.                  u:object_r:system_prop:s0
 sys.                    u:object_r:system_prop:s0
+sys.init.userspace_reboot   u:object_r:userspace_reboot_prop:s0
 sys.cppreopt            u:object_r:cppreopt_prop:s0
 sys.linker.             u:object_r:linker_prop:s0
 sys.lpdumpd             u:object_r:lpdumpd_prop:s0