zlib: fix raw inflate with custom dictionary

Moves inflateSetDictionary right after inflateInit2 when mode is
INFLATERAW, since without the wrapper in appears zlib won't return
Z_NEED_DICT as it would otherwise, and will thus attempt inflating
without the dictionary, leading to an error.

Fixes: https://github.com/nodejs/node/issues/8507
PR-URL: https://github.com/nodejs/node/pull/8512


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>