MDEV-32926 mysql_install_db_win fails on buildbot

In mysql_install_db_win_admin test, dump bootstrap output in case of
bootstrap failure.

mysql-test/main/mysql_install_db_win_admin.result

 use mysql;
-Running bootstrap
-Creating my.ini file
-Removing default user
-Allowing remote access for user root
-Setting root password
-Creation of the database was successful
 # Kill the server
 # restart: --datadir=MYSQLTEST_VARDIR/tmp/ddir
 connect  root,localhost,root,wrongpass,mysql;

mysql-test/main/mysql_install_db_win_admin.test

@@ -6,12 +6,15 @@
 # and start server from this directory.
 let $ddir= $MYSQLTEST_VARDIR/tmp/ddir;
 use mysql;
-exec $MYSQL_INSTALL_DB_EXE --datadir=$ddir --password=foo -R;
+--disable_result_log
+exec $MYSQL_INSTALL_DB_EXE --datadir=$ddir --password=foo --verbose-bootstrap -R;
+--enable_result_log
 --source include/kill_mysqld.inc
 let $restart_parameters=--datadir=$ddir;
 --source include/start_mysqld.inc
 
 # Check that connect with wrong password succeeds
+# (because it can alternatively connect with GSSAPI as admin)
 connect (root,localhost,root,wrongpass,mysql);
 
 --source include/kill_mysqld.inc