MINOR: server: Only defined conn_complete_server if USE_OPENSSL is set.

conn_complete_server() is only used when using ALPN/NPN, so only define it
if USE_OPENSSL is set.

src/backend.c

@@ -1035,6 +1035,7 @@ static void assign_tproxy_address(struct stream *s)
 #endif
 }
 
+#ifdef USE_OPENSSL
 /*
  * Pick the right mux once the connection is established, we should now have
  * an alpn if available, so we are now able to choose.
@@ -1069,6 +1070,7 @@ fail:
 	conn_free(conn);
 	return -1;
 }
+#endif
 
 
 /*