Add ro.sys.safemode property.

Bug: 28008032
Change-Id: I29e076ee9c62a0fb3b386f79509935a1961f95e1
diff --git a/property_contexts b/property_contexts
index 504e1a0..1329854 100644
--- a/property_contexts
+++ b/property_contexts
@@ -44,6 +44,7 @@
 persist.mmc.            u:object_r:mmc_prop:s0
 persist.sys.            u:object_r:system_prop:s0
 persist.sys.safemode    u:object_r:safemode_prop:s0
+ro.sys.safemode         u:object_r:safemode_prop:s0
 persist.sys.audit_safemode      u:object_r:safemode_prop:s0
 persist.service.        u:object_r:system_prop:s0
 persist.service.bdroid. u:object_r:bluetooth_prop:s0