address a file descriptor leak

lib/storage/file.js

@@ -779,9 +779,11 @@ const messageBin = (env, chanName, msgBin, cb) => {
         chan.writeStream.write(msgBin, function () {
             chan.onError.splice(chan.onError.indexOf(complete), 1);
             complete();
+// It seems like this reintroduces a file descriptor leak
             if (chan.onError.length) { return; }
             if (chan.delayClose && chan.delayClose.clear) {
                 chan.delayClose.clear();
+                destroyStream(chan.writeStream, chanName);
                 delete env.channels[chanName];
             }
         });