Upstream: add missing thread_exit()

Undo FreeBSD wrapper for thread_create() added to call thread_exit.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Jorgen Lundman <lundman@lundman.net>
Closes #10314

module/zfs/dmu_send.c

@@ -1319,6 +1319,8 @@ redact_list_thread(void *arg)
 	record = range_alloc(DATA, 0, 0, 0, B_TRUE);
 	bqueue_enqueue_flush(&rlt_arg->q, record, sizeof (*record));
 	spl_fstrans_unmark(cookie);
+
+	thread_exit();
 }
 
 /*

module/zfs/vdev_initialize.c

@@ -558,6 +558,8 @@ vdev_initialize_thread(void *arg)
 	vd->vdev_initialize_thread = NULL;
 	cv_broadcast(&vd->vdev_initialize_cv);
 	mutex_exit(&vd->vdev_initialize_lock);
+
+	thread_exit();
 }
 
 /*

module/zfs/vdev_removal.c

@@ -1595,6 +1595,8 @@ spa_vdev_remove_thread(void *arg)
 		ASSERT0(range_tree_space(svr->svr_allocd_segs));
 		vdev_remove_complete(spa);
 	}
+
+	thread_exit();
 }
 
 void

module/zfs/vdev_trim.c

@@ -896,6 +896,8 @@ vdev_trim_thread(void *arg)
 	vd->vdev_trim_thread = NULL;
 	cv_broadcast(&vd->vdev_trim_cv);
 	mutex_exit(&vd->vdev_trim_lock);
+
+	thread_exit();
 }
 
 /*