iproto: accept MP_STR *and* MP_BIN as type for authentication scramble
iproto: accept MP_STR *and* MP_BIN as type for authentication scramble

Accept MP_STR *and* MP_BIN as type for authentication scramble key
in IPROTO_AUTH packet.
Some codecs automatically pack non-utf-8 strings as MP_BIN. A scramble
is just an octect stream, so can (by chance) be both a utf-8 stream
and a binary stream, depending on the random seed.

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