Merge pull request #4725 from yang-g/destroy_reader

destroy reader after using it

src/cpp/util/byte_buffer.cc

@@ -69,6 +69,7 @@ void ByteBuffer::Dump(std::vector<Slice>* slices) const {
   while (grpc_byte_buffer_reader_next(&reader, &s)) {
     slices->push_back(Slice(s, Slice::STEAL_REF));
   }
+  grpc_byte_buffer_reader_destroy(&reader);
 }
 
 size_t ByteBuffer::Length() const {
@@ -88,4 +89,4 @@ ByteBuffer& ByteBuffer::operator=(const ByteBuffer& buf) {
   return *this;
 }
 
-}  // namespace grpc
+}  // namespace grpc