Chase malloc() change by removing lg_chunk malloc_conf settings.

In jemalloc 5, there are no longer chunks, and as configured on
FreeBSD (the "retain" option defaults to false), the mmap()
requests are precisely sized for the specific needs, which means
the virtual memory overhead should be lower for small applications.

Reviewed by:	jasone, ian
Differential Revision:	https://reviews.freebsd.org/D11366

usr.sbin/watchdogd/watchdogd.c

@@ -111,14 +111,6 @@ static struct option longopts[] = {
 	{ NULL, 0, NULL, 0}
 };
 
-/*
- * Ask malloc() to map minimum-sized chunks of virtual address space at a time,
- * so that mlockall() won't needlessly wire megabytes of unused memory into the
- * process.  This must be done using the malloc_conf string so that it gets set
- * up before the first allocation, which happens before entry to main().
- */
-const char * malloc_conf = "lg_chunk:0";
-
 /*
  * Periodically pat the watchdog, preventing it from firing.
  */