Replace zed's use of malloc with calloc

When zed allocates memory via malloc(), it typically follows that
with a memset().  However, calloc() implementations can often perform
optimizations when zeroing memory:

https://stackoverflow.com/questions/2688466/why-mallocmemset-is-slower-than-calloc

This commit replaces zed's use of malloc() with calloc().

Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2736

cmd/zed/zed_conf.c

@@ -51,12 +51,10 @@ zed_conf_create(void)
 {
 	struct zed_conf *zcp;
 
-	zcp = malloc(sizeof (*zcp));
+	zcp = calloc(1, sizeof (*zcp));
 	if (!zcp)
 		goto nomem;
 
-	memset(zcp, 0, sizeof (*zcp));
-
 	zcp->syslog_facility = LOG_DAEMON;
 	zcp->min_events = ZED_MIN_EVENTS;
 	zcp->max_events = ZED_MAX_EVENTS;

cmd/zed/zed_exec.c

@@ -61,7 +61,7 @@ _zed_exec_create_env(zed_strings_t *zsp)
 	for (q = zed_strings_first(zsp); q; q = zed_strings_next(zsp))
 		buflen += strlen(q) + 1;
 
-	buf = malloc(buflen);
+	buf = calloc(1, buflen);
 	if (!buf)
 		return (NULL);
 

cmd/zed/zed_strings.c

@@ -82,11 +82,10 @@ zed_strings_create(void)
 {
 	zed_strings_t *zsp;
 
-	zsp = malloc(sizeof (*zsp));
+	zsp = calloc(1, sizeof (*zsp));
 	if (!zsp)
 		return (NULL);
 
-	memset(zsp, 0, sizeof (*zsp));
 	avl_create(&zsp->tree, _zed_strings_node_compare,
 	    sizeof (zed_strings_node_t), offsetof(zed_strings_node_t, node));
 
@@ -131,11 +130,10 @@ zed_strings_add(zed_strings_t *zsp, const char *s)
 		return (-1);
 	}
 	len = sizeof (zed_strings_node_t) + strlen(s) + 1;
-	np = malloc(len);
+	np = calloc(1, len);
 	if (!np)
 		return (-1);
 
-	memset(np, 0, len);
 	assert((char *) np->string + strlen(s) < (char *) np + len);
 	(void) strcpy(np->string, s);
 	avl_add(&zsp->tree, np);