sometimes with prepared+query_cache

Analysis
=========
Prepare and execute flow (Client API) with CURSOR_TYPE_READ_ONLY
followed by CURSOR_TYPE_NO_CURSOR fails while fetching
result from a query cache enabled server.

First prepare and execute with CURSOR_TYPE_NO_CURSOR
saves the query result to query cache. Second request
with CURSOR_TYPE_NO_CURSOR will hit query cache and return
without considering cursor status. This leads to client
requesting for cursor fetch and results in error from server
as there is no open cursor associated with the statement.

Fix:
=======
Execution with CURSOR_TYPE_READ_ONLY does not use cached
result. There is no point in caching such querries. Marked
safe_to_cache_query=0 for cursor enabled query.