Fix freeing of dyn_data and temp metadata block buffers on read cancel

A regression test would also be fun

src/blockstore/v1/read.cpp

@@ -552,8 +552,6 @@ int blockstore_impl_t::dequeue_read(blockstore_op_t *read_op)
 undo_read:
     // need to wait. undo added requests, don't dequeue op
     release_clean(read_op);
-    if (dsk.csum_block_size > dsk.bitmap_granularity)
-    {
     for (auto & vec: rv)
     {
         if ((vec.copy_flags & COPY_BUF_CSUM_FILL) && vec.buf)
@@ -567,7 +565,6 @@ undo_read:
             vec.dyn_data = NULL;
         }
     }
-    }
     rv.clear();
     return 0;
 }