crypto: remove BIO_set_shutdown

I've not been able to find any reason for calling
BIO_set_shutdown(bio, 1). This is done by default for the following
versions of OpenSSL:

https://github.com/openssl/openssl/blob/OpenSSL_1_1_0/
crypto/bio/bio_lib.c#L26

https://github.com/openssl/openssl/blob/OpenSSL_1_0_1/
crypto/bio/bio_lib.c#L90

https://github.com/openssl/openssl/blob/OpenSSL_1_0_2/
crypto/bio/bio_lib.c#L88

https://github.com/openssl/openssl/blob/OpenSSL_1_0_0/
crypto/bio/bio_lib.c#L90

This commit removes the call and the comment.

PR-URL: #17542
Reviewed-By: Ben Noordhuis <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>

Author: danbev

src/node_crypto_bio.cc

@@ -68,8 +68,6 @@ void NodeBIO::AssignEnvironment(Environment* env) {
 int NodeBIO::New(BIO* bio) {
   BIO_set_data(bio, new NodeBIO());
 
-  // XXX Why am I doing it?!
-  BIO_set_shutdown(bio, 1);
   BIO_set_init(bio, 1);
 
   return 1;