This enables server build for Ubuntu 18.04 LTS, the ldiskfs
patches are based on Gael's 4.12 support,
they apply to kernel versions 4.15.0-20.21 to 4.15.0-23.25

There's also a small fix to make dpkg happy when installing
lustre packages which requires lustre-client-utils.

Test-Parameters: clientdistro=ubuntu1604 trivial
Signed-off-by: Li Dongyang <dongyangli@ddn.com>
Signed-off-by: Gael Delbary <gael.delbary@cea.fr>
Change-Id: I65e1a5ee0d17115f23ba071ff1ab23b4fb22e78f
Reviewed-on: https://review.whamcloud.com/32613


Tested-by: Jenkins
Reviewed-by: Quentin Bouget <quentin.bouget@cea.fr>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Yang Sheng <ys@whamcloud.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>