Fix pg_upgrade to create pg_authid restore functions in the 'postgres'

database, not in the os-user database, per report from Magnus.

contrib/pg_upgrade/pg_upgrade.c

@@ -50,6 +50,9 @@ static void set_frozenxids(void);
 static void setup(char *argv0, bool live_check);
 static void cleanup(void);
 
+/* This is the database used by pg_dumpall to restore global tables */
+#define GLOBAL_DUMP_DB	"postgres"
+
 ClusterInfo old_cluster, new_cluster;
 OSInfo		os_info;
 
@@ -226,10 +229,10 @@ prepare_new_databases(void)
 	prep_status("Creating databases in the new cluster");
 
 	/*
-	 *	Install support functions in the database accessed by
-	 *	GLOBALS_DUMP_FILE because it can preserve pg_authid.oid.
+	 *	Install support functions in the global-restore database
+	 *	to preserve pg_authid.oid.
 	 */
-	install_support_functions_in_new_db(os_info.user);
+	install_support_functions_in_new_db(GLOBAL_DUMP_DB);
 
 	/*
 	 * We have to create the databases first so we can install support
@@ -266,7 +269,7 @@ create_new_objects(void)
 		DbInfo	   *new_db = &new_cluster.dbarr.dbs[dbnum];
 
 		/* skip db we already installed */
-		if (strcmp(new_db->db_name, os_info.user) != 0)
+		if (strcmp(new_db->db_name, GLOBAL_DUMP_DB) != 0)
 			install_support_functions_in_new_db(new_db->db_name);
 	}
 	check_ok();