Extra engines enabled through additional config are not loaded on first installation

We have some engines which are installed from separate packages. When it happens, they also install additional configs with plugin-load-add=ha_engine options.

However, upon initial installation apparently these config files are created after the server is started; so, upon first automatic startup after installation the server still does not have them, which seems confusing. I suppose it needs to be fixed somehow.

I've set the affected version to 10.2 because that's where I encountered it, but probably other ones are also affected.

To reproduce:

• enable MariaDB repo, e.g. 10.2
• run apt-get install mariadb-server mariadb-plugin-rocksdb
• check that the server is running, but it doesn't have RocksDB
• restart the server – now RocksDB is there