Set dictionary ID in ZSTD_initCStream_usingCDict()

Set dictionary ID in ZSTD_initCStream_usingCDict()

When porting python-zstandard to use ZSTD_initCStream_usingCDict()
so compression dictionaries could be reused, an automated test
failed due to compressed content changing.

I tracked this down to ZSTD_initCStream_usingCDict() not
setting the dictID field of the ZSTD_CCtx attached to the
ZSTD_CStream instance.

I'm not 100% convinced this is the correct or full solution,
as I'm still seeing one automated test failing with this change.