Allow transform destroy to flush on an infected file.
Allow transform destroy to flush on an infected file.

We've bolted ClamScan into Meteor.  On testing an infected file, we see the following error.  The above corrects it.
```
W20200120-14:47:30.650(8)? (STDERR) Error: stream.push() after EOF
W20200120-14:47:30.650(8)? (STDERR)     at readableAddChunk (_stream_readable.js:240:30)
W20200120-14:47:30.650(8)? (STDERR)     at NodeClamTransform.Readable.push (_stream_readable.js:208:10)
W20200120-14:47:30.651(8)? (STDERR)     at NodeClamTransform.Transform.push (_stream_transform.js:147:32)
W20200120-14:47:30.651(8)? (STDERR)     at NodeClamTransform._flush (/home/cui/loudspeed-admin/.meteor/local/isopacks/loudspeed_node-modules/npm/node_modules/clamscan/NodeClamTransform.js:38:14)
W20200120-14:47:30.651(8)? (STDERR)     at NodeClamTransform.prefinish (_stream_transform.js:137:10)
W20200120-14:47:30.651(8)? (STDERR)     at emitNone (events.js:106:13)
W20200120-14:47:30.651(8)? (STDERR)     at NodeClamTransform.emit (events.js:208:7)
W20200120-14:47:30.651(8)? (STDERR)     at prefinish (_stream_writable.js:602:14)
W20200120-14:47:30.651(8)? (STDERR)     at finishMaybe (_stream_writable.js:610:5)
W20200120-14:47:30.651(8)? (STDERR)     at endWritable (_stream_writable.js:621:3)
W20200120-14:47:30.651(8)? (STDERR)     at NodeClamTransform.Writable.end (_stream_writable.js:572:5)
W20200120-14:47:30.652(8)? (STDERR)     at NodeClamTransform.Duplex._destroy (_stream_duplex.js:118:8)
W20200120-14:47:30.652(8)? (STDERR)     at NodeClamTransform.Transform._destroy (_stream_transform.js:196:29)
W20200120-14:47:30.652(8)? (STDERR)     at NodeClamTransform.destroy (internal/streams/destroy.js:32:8)
W20200120-14:47:30.652(8)? (STDERR)     at handle_error (/home/cui/loudspeed-admin/.meteor/local/isopacks/loudspeed_node-modules/npm/node_modules/clamscan/index.js:927:44)
W20200120-14:47:30.652(8)? (STDERR)     at Socket._clamav_socket.on.on.on.on.on.on.cv_chunk (/home/cui/loudspeed-admin/.meteor/local/isopacks/loudspeed_node-modules/npm/node_modules/clamscan/index.js:1014:41)
```
kylefarris/clamscan