gh-584: box_free() is called even if box is not initialized
gh-584: box_free() is called even if box is not initialized

Do stuff in box_free() only if initialization has succeeded.

ocelot-inc/tarantool,vasilenkomike/tarantool,condor-the-bird/tarantool,condor-the-bird/tarantool,guard163/tarantool,KlonD90/tarantool,ocelot-inc/tarantool,rtsisyk/tarantool,KlonD90/tarantool,mejedi/tarantool,condor-the-bird/tarantool,vasilenkomike/tarantool,Sannis/tarantool,rtsisyk/tarantool,guard163/tarantool,guard163/tarantool,vasilenkomike/tarantool,guard163/tarantool,Sannis/tarantool,ocelot-inc/tarantool,Sannis/tarantool,vasilenkomike/tarantool,ocelot-inc/tarantool,Sannis/tarantool,mejedi/tarantool,KlonD90/tarantool,vasilenkomike/tarantool,Sannis/tarantool,rtsisyk/tarantool,condor-the-bird/tarantool,rtsisyk/tarantool,condor-the-bird/tarantool,mejedi/tarantool,KlonD90/tarantool,KlonD90/tarantool,guard163/tarantool,mejedi/tarantool