Remove spurious call to 'sync'; we don't need to flush all disk caches

on the system to cleanly unmount a partition.

debian/changelog

@@ -1,3 +1,10 @@
+livecd-rootfs (2.459) UNRELEASED; urgency=medium
+
+  * Remove spurious call to 'sync'; we don't need to flush all disk caches
+    on the system to cleanly unmount a partition.
+
+ -- Steve Langasek <steve.langasek@ubuntu.com>  Tue, 19 Sep 2017 13:15:33 -0700
+
 livecd-rootfs (2.458) artful; urgency=medium
 
   * Move default netplan config for server-live image to where hook will

live-build/ubuntu-cpc/hooks/033-disk-image-uefi.binary

@@ -110,7 +110,6 @@ install_grub() {
     chroot mountpoint apt-get -y clean
 
     rm mountpoint/tmp/device.map
-    sync
     umount mountpoint/boot/efi
     mount
     umount_partition mountpoint