Import patches-unapplied version 2.455 to ubuntu/artful-proposed

Imported using git-ubuntu import.

Changelog parent: efbd6fd1c6

New changelog entries:
  * Restore the call to 'umount -R $mountpoint' from umount_partition,
    accidentally dropped in previous upload.

debian/changelog

@@ -1,3 +1,10 @@
+livecd-rootfs (2.455) artful; urgency=medium
+
+  * Restore the call to 'umount -R $mountpoint' from umount_partition,
+    accidentally dropped in previous upload.
+
+ -- Steve Langasek <steve.langasek@ubuntu.com>  Wed, 13 Sep 2017 12:50:10 -0700
+
 livecd-rootfs (2.454) artful; urgency=medium
 
   [ Steve Langasek ]

live-build/functions

@@ -152,6 +152,7 @@ EOF
 umount_partition() {
     local mountpoint=${1}
     teardown_mountpoint $mountpoint
+    umount -R $mountpoint
     udevadm settle
 
     if [ -n "${rootfs_dev_mapper}" -a -b "${rootfs_dev_mapper}" ]; then