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/service_contexts b/private/service_contexts
index 51161c0..808edcc 100644
--- a/private/service_contexts
+++ b/private/service_contexts
@@ -16,6 +16,7 @@
 android.os.UpdateEngineStableService      u:object_r:update_engine_stable_service:s0
 android.security.identity                 u:object_r:credstore_service:s0
 android.security.keystore                 u:object_r:keystore_service:s0
+android.security.keystore2                u:object_r:keystore_service:s0
 android.service.gatekeeper.IGateKeeperService    u:object_r:gatekeeper_service:s0
 app_binding                               u:object_r:app_binding_service:s0
 app_integrity                             u:object_r:app_integrity_service:s0