Handle failed Finish() in SST file writer

Summary:
The assertion in Abandon() fails when called after Finish() fails. Finish() already closes the builder so there's no need to call Abandon().
Closes https://github.com/facebook/rocksdb/pull/1901

Differential Revision: D4601373

Pulled By: ajkr

fbshipit-source-id: e5678be

table/sst_file_writer.cc

@@ -189,10 +189,7 @@ Status SstFileWriter::Finish(ExternalSstFileInfo* file_info) {
     if (s.ok()) {
       s = r->file_writer->Close();
     }
-  } else {
-    r->builder->Abandon();
   }
-
   if (!s.ok()) {
     r->ioptions.env->DeleteFile(r->file_info.file_path);
   }