Do nothing in SIGUSR1 signal handler if box is uninitialized.
Do nothing in SIGUSR1 signal handler if box is uninitialized.

Fixes gh-1624.

ocelot-inc/tarantool,ocelot-inc/tarantool,mejedi/tarantool,mejedi/tarantool,rtsisyk/tarantool,ocelot-inc/tarantool,rtsisyk/tarantool,rtsisyk/tarantool,mejedi/tarantool,mejedi/tarantool,ocelot-inc/tarantool,rtsisyk/tarantool