BIO: at the end of BIO_new, declare the BIO inited if no create method present

Without this, every BIO implementation is forced to have a create
method, just to set bio->init = 1.
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5223)

crypto/bio/bio_lib.c

@@ -98,6 +98,8 @@ BIO *BIO_new(const BIO_METHOD *method)
         CRYPTO_THREAD_lock_free(bio->lock);
         goto err;
     }
+    if (method->create == NULL)
+        bio->init = 1;
 
     return bio;