BUG/MINOR: peers/config: always fill the bind_conf's argument

Some generic frontend errors mention the bind_conf by its name as
"bind '%s'", but if this is used on peers "bind" lines it shows
"(null)" because the argument is set to NULL in the call to
bind_conf_uniq_alloc() instead of passing the argument. Fortunately
that's trivial to fix.

This may be backported to older versions.

src/cfgparse.c

@@ -703,7 +703,7 @@ int cfg_parse_peers(const char *file, int linenum, char **args, int kwm)
 		}
 
 		bind_conf = bind_conf_uniq_alloc(curpeers->peers_fe, file, linenum,
-		                                 NULL, xprt_get(XPRT_RAW));
+		                                 args[1], xprt_get(XPRT_RAW));
 		if (*args[0] == 'b') {
 			struct listener *l;