src: don't check failure with ERR_peek_error()

It's possible there is already an existing error on OpenSSL's error
stack that is unrelated to the EVP_DigestInit_ex() operation we just
executed.

Fixes: https://github.com/nodejs/node/issues/4221
PR-URL: https://github.com/nodejs/node/pull/4731
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Fedor Indutny <fedor@indutny.com>

src/node_crypto.cc

@@ -3440,8 +3440,7 @@ bool Hash::HashInit(const char* hash_type) {
   if (md_ == nullptr)
     return false;
   EVP_MD_CTX_init(&mdctx_);
-  EVP_DigestInit_ex(&mdctx_, md_, nullptr);
-  if (0 != ERR_peek_error()) {
+  if (EVP_DigestInit_ex(&mdctx_, md_, nullptr) <= 0) {
     return false;
   }
   initialised_ = true;