Format 0 bytes as 0b, be consistent about internal byte arguments

0 bytes are not a bogus number

bin/varnishd/mgt/mgt_main.c

@@ -443,12 +443,12 @@ init_params(struct cli *cli)
 #endif
 
 	low = sysconf(_SC_THREAD_STACK_MIN);
-	MCF_ParamConf(MCF_MINIMUM, "thread_pool_stack", "%jd", (intmax_t)low);
+	MCF_ParamConf(MCF_MINIMUM, "thread_pool_stack", "%jdb", (intmax_t)low);
 
 	def = 48 * 1024;
 	if (def < low)
 		def = low;
-	MCF_ParamConf(MCF_DEFAULT, "thread_pool_stack", "%jd", (intmax_t)def);
+	MCF_ParamConf(MCF_DEFAULT, "thread_pool_stack", "%jdb", (intmax_t)def);
 
 	MCF_ParamConf(MCF_MAXIMUM, "thread_pools", "%d", MAX_THREAD_POOLS);
 

bin/varnishd/mgt/mgt_param_tweak.c

@@ -223,7 +223,7 @@ fmt_bytes(struct vsb *vsb, uintmax_t t)
 {
 	const char *p;
 
-	if (t & 0xff) {
+	if (t == 0 || t & 0xff) {
 		VSB_printf(vsb, "%jub", t);
 		return;
 	}