Print iostat headers every time terminal fills.

Each time terminal fills zpool iostat will print headers.
If -n flag is passed this behavior will be supressed.

Signed-off-by: Damian Wojslaw <damian@wojslaw.pl>

cmd/zpool/zpool_main.c

@@ -4748,7 +4748,7 @@ get_namewidth_iostat(zpool_handle_t *zhp, void *data)
  *	-w	Display latency histograms
  *	-r	Display request size histogram
  *	-T	Display a timestamp in date(1) or Unix format
- *	-n  Only print headers once
+ *	-n>·Only print headers once
  *
  * This command can be tricky because we want to be able to deal with pool
  * creation/destruction as well as vdev configuration changes.  The bulk of this
@@ -4764,8 +4764,8 @@ zpool_do_iostat(int argc, char **argv)
 	int npools;
 	float interval = 0;
 	unsigned long count = 0;
-    struct winsize win;
-    int winheight = 24;         // Default number of terminal rows
+>···struct winsize win;
+>···int winheight = 24;         // Default number of terminal rows
 	zpool_list_t *list;
 	boolean_t verbose = B_FALSE;
 	boolean_t latency = B_FALSE, l_histo = B_FALSE, rq_histo = B_FALSE;
@@ -4774,7 +4774,7 @@ zpool_do_iostat(int argc, char **argv)
 	boolean_t guid = B_FALSE;
 	boolean_t follow_links = B_FALSE;
 	boolean_t full_name = B_FALSE;
-    boolean_t headers_once = B_FALSE;
+>···boolean_t headers_once = B_FALSE;
 	iostat_cbdata_t cb = { 0 };
 	char *cmd = NULL;
 
@@ -4848,9 +4848,9 @@ zpool_do_iostat(int argc, char **argv)
 		case 'y':
 			omit_since_boot = B_TRUE;
 			break;
-        case 'n':
-            headers_once = B_TRUE;
-            break;
+>···>···>···case 'n':
+>···>···>···headers_once = B_TRUE;
+>···>···>···break;
 		case 'h':
 			usage(B_FALSE);
 			break;
@@ -4860,7 +4860,7 @@ zpool_do_iostat(int argc, char **argv)
 				exit(0);
 			} else {
 				fprintf(stderr,
-				    gettext("invalid option '%c'\n"), optopt);
+				>···gettext("invalid option '%c'\n"), optopt);
 			}
 			usage(B_FALSE);
 		}
@@ -5013,8 +5013,8 @@ zpool_do_iostat(int argc, char **argv)
 	}
 
 
-    if(ioctl(1,TIOCGWINSZ, &win) != -1 && win.ws_row > 0)
-        winheight = win.ws_row;
+>···if(ioctl(1,TIOCGWINSZ, &win) != -1 && win.ws_row > 0)
+>···>···winheight = win.ws_row;
 
 	for (;;) {
 		if ((npools = pool_list_count(list)) == 0)