The two I_S plugins SPIDER_ALLOC_MEM and SPIDER_WRAPPER_PROTOCOL
only makes sense if the main SPIDER plugin is installed. Further,
SPIDER_ALLOC_MEM requires a mutex that requires SPIDER init to fill
the table.

We also update the spider init query to override
--transaction_read_only=on so that it does not affect the spider init.

Also fixed error handling in spider_db_init() so that failure in
spider table init does not result in memory leak