Fixed small memory leak in ereport handling

One pre-check in zfs_ereport_start() was being called after
the nvlists were being allocated. This simply corrects that
issue.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tom Caputi <tcaputi@datto.com>
Closes openzfs#6140

module/zfs/zfs_fm.c

@@ -210,6 +210,12 @@ zfs_ereport_start(nvlist_t **ereport_out, nvlist_t **detector_out,
 	    (vd->vdev_remove_wanted || vd->vdev_state == VDEV_STATE_REMOVED))
 		return;
 
+	if ((strcmp(subclass, FM_EREPORT_ZFS_DELAY) == 0) &&
+	    (zio != NULL) && (!zio->io_timestamp)) {
+		/* Ignore bogus delay events */
+		return;
+	}
+
 	if ((ereport = fm_nvlist_create(NULL)) == NULL)
 		return;
 
@@ -218,12 +224,6 @@ zfs_ereport_start(nvlist_t **ereport_out, nvlist_t **detector_out,
 		return;
 	}
 
-	if ((strcmp(subclass, FM_EREPORT_ZFS_DELAY) == 0) &&
-	    (zio != NULL) && (!zio->io_timestamp)) {
-		/* Ignore bogus delay events */
-		return;
-	}
-
 	/*
 	 * Serialize ereport generation
 	 */