Add policy for ping.

Change-Id: I168f681d8c67f470b6e639f0b1bf39346c4eb396
diff --git a/file_contexts b/file_contexts
index 3d885b1..15f9f59 100644
--- a/file_contexts
+++ b/file_contexts
@@ -148,6 +148,7 @@
 /system/etc/dhcpcd(/.*)? u:object_r:dhcp_system_file:s0
 /system/xbin/su		u:object_r:su_exec:s0
 /system/vendor/bin/gpsd u:object_r:gpsd_exec:s0
+/system/bin/ping    u:object_r:ping_exec:s0
 #############################
 # Vendor files
 #