Set the container field of aconfig flags

Test: m
Bug: 312769710
Change-Id: I366717c7139886e30360914256ad7710da5095e9
diff --git a/keystore2/aconfig/flags.aconfig b/keystore2/aconfig/flags.aconfig
index 133c4ab..b67bc6c 100644
--- a/keystore2/aconfig/flags.aconfig
+++ b/keystore2/aconfig/flags.aconfig
@@ -1,4 +1,5 @@
 package: "android.security.keystore2"
+container: "system"
 
 flag {
   name: "wal_db_journalmode_v3"