Old default vsl_buffer for 32 bit

After 88698015 broke 32 bit, we need to adjust the default(s) which
are special cased for 32 bit in mgt_param.c. Instead of increasing
things, we make sure the old default vsl_buffer of 4k is maintained.

bin/varnishd/mgt/mgt_param.c

@@ -672,6 +672,7 @@ MCF_InitParams(struct cli *cli)
 		MCF_ParamConf(MCF_DEFAULT, "http_resp_size", "8k");
 		MCF_ParamConf(MCF_DEFAULT, "http_req_size", "12k");
 		MCF_ParamConf(MCF_DEFAULT, "gzip_buffer", "4k");
+		MCF_ParamConf(MCF_DEFAULT, "vsl_buffer", "4k");
 		MCF_ParamConf(MCF_MAXIMUM, "vsl_space", "1G");
 		def = 52 * 1024;
 	}