Remove redundant check from SSL_shutdown

The SSL object was being deref'd and then there was a later redundant check
to see if it is NULL. We assume all SSL_foo functions pass a non NULL SSL
object and do not check it.
Reviewed-by: NTim Hudson <tjh@openssl.org>

ssl/ssl_lib.c

@@ -990,7 +990,7 @@ int SSL_shutdown(SSL *s)
         return -1;
     }
 
-    if ((s != NULL) && !SSL_in_init(s))
+    if (!SSL_in_init(s))
         return (s->method->ssl_shutdown(s));
     else
         return (1);