vinyl: free all indexes on shutdown
vinyl: free all indexes on shutdown

Freeing all memory on shutdown would let us make debugging tools like
valgrind happy.

mejedi/tarantool,mejedi/tarantool,rtsisyk/tarantool,rtsisyk/tarantool,rtsisyk/tarantool,mejedi/tarantool,mejedi/tarantool,rtsisyk/tarantool