Fix windows thread stop code
Fix windows thread stop code

The windows thread stop code was erroneously not just deleting the thread
local variable on thread stop, but also deleting the thread local *key*
(thus removing thread local data for *all* threads in one go!).

Reviewed-by: Rich Salz <c04971a99e5a9ee80eaab4b1deb37e845b0bd697@openssl.org>

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl