quic_multistream_test: fix undefined symbol snprintf with VS2010

quic_multistream_test: fix undefined symbol snprintf with VS2010

As snprintf is not available everywhere, use BIO_snprintf instead.

Fixes:
        IF EXIST test\quic_multistream_test.exe.manifest DEL /F /Q test\quic_multistream_test.exe.manifest
        "link" /nologo /debug setargv.obj /subsystem:console /opt:ref  /nologo /debug @V:\_tmp\nm4.tmp
quic_multistream_test-bin-quic_multistream_test.obj : error LNK2019: unresolved external symbol _snprintf referenced in function _helper_init
test\quic_multistream_test.exe : fatal error LNK1120: 1 unresolved externals
NMAKE : fatal error U1077: '"E:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\BIN\link.EXE"' : return code '0x460'

Signed-off-by: Georgi Valkov <gvalkov@gmail.com>
Reviewed-by: Paul Dale <ppzgs1@gmail.com>
Reviewed-by: Tom Cosgrove <tom.cosgrove@arm.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/24369)