Add keystore user_changed permission

user_changed will be used for state change methods around android user
creation/deletion.

(cherry-picked from commit 520bb816)

Change-Id: I295ca9adfc4907b5d7bcf0555f6e5a9a3379635b

access_vectors

@@ -910,6 +910,7 @@ class keystore_key
 	sync_uid
 	password_uid
 	add_auth
+	user_changed
 }
 
 class debuggerd

system_app.te

@@ -73,6 +73,7 @@ allow system_app keystore:keystore_key {
 	grant
 	duplicate
 	clear_uid
+	user_changed
 };
 
 control_logd(system_app)

system_server.te

@@ -401,6 +401,7 @@ allow system_server keystore:keystore_key {
 	sync_uid
 	password_uid
 	add_auth
+	user_changed
 };
 
 # Allow system server to search and write to the persistent factory reset