Fix a regression introduced in r344569

Import a fix from illumos (thanks Toomas Soomas for pointing at it)

See https://www.illumos.org/issues/10205 for more details
Illumos commit: 247b7da039

Submitted by:	jack@gandi.net
Reported by:	cy
Reviewed by:	tsoome, cy, bapt
Obtained from:	Illumos

cddl/contrib/opensolaris/cmd/zfs/zfs_main.c

@@ -6119,9 +6119,6 @@ report_mount_progress(int current, int total)
 	time_t now = time(NULL);
 	char info[32];
 
-	/* report 1..n instead of 0..n-1 */
-	++current;
-
 	/* display header if we're here for the first time */
 	if (current == 1) {
 		set_progress_header(gettext("Mounting ZFS filesystems"));