Volume.FileChannel: ensure available did not increase file size. Fix #502.
Volume.FileChannel: ensure available did not increase file size. Fix #502.

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