AsyncWriteEngine: remove outdated code
AsyncWriteEngine: remove outdated code

jankotek/mapdb,pettermahlen/mapdb,morfeo8marc/mapdb,hangum/mapdb,jankotek/MapDB,binarytemple/mapdb,jankotek/MapDB,sumit784/mapdb,olupas/MapDB,mebigfatguy/mapdb,ffjiao/mapdb,jankotek/mapdb,ringoluo/mapdb,mebigfatguy/mapdb,codeaudit/mapdb,olupas/MapDB,SleimanJneidi/mapdb,lamfire/mapdb,cocosli/mapdb