sftp_close_handle: packet list is generic

Fix comment, simplify the loop logic

src/sftp.c

@@ -1933,17 +1933,15 @@ sftp_close_handle(LIBSSH2_SFTP_HANDLE *handle)
         if(handle->u.file.data)
             LIBSSH2_FREE(session, handle->u.file.data);
     }
-    /* remove pending write chunks */
+    /* remove pending packets, if any */
-    do {
     chunk = _libssh2_list_first(&handle->packet_list);
-        if(chunk) {
+    while(chunk) {
         struct sftp_write_chunk *next =
             _libssh2_list_next(&chunk->node);
         _libssh2_list_remove(&chunk->node);
         LIBSSH2_FREE(session, chunk);
         chunk = next;
     }
-    } while(chunk);
 
     handle->close_state = libssh2_NB_state_idle;