Prepare sepolicy for launching Keystore 2.0 service

This patch labels /system/bin/keystore2 as a keystore executable and
allows keystore to register "system.security.keystore2" with the service
manager.

Bug: 160623310
Test: None
Change-Id: I1812e565438c2b8ae55c8d10bcc8450d27717697
diff --git a/private/file_contexts b/private/file_contexts
index 08e9e2f..c76ff3d 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -259,6 +259,7 @@
 /system/bin/art_apex_boot_integrity   u:object_r:art_apex_boot_integrity_exec:s0
 /system/bin/credstore	u:object_r:credstore_exec:s0
 /system/bin/keystore	u:object_r:keystore_exec:s0
+/system/bin/keystore2	u:object_r:keystore_exec:s0
 /system/bin/fingerprintd u:object_r:fingerprintd_exec:s0
 /system/bin/gatekeeperd u:object_r:gatekeeperd_exec:s0
 /system/bin/tombstoned u:object_r:tombstoned_exec:s0