LU-1706 build: Fixes for debian build system with Ubuntu 12.04+

LU-1706 build: Fixes for debian build system with Ubuntu 12.04+

Propagate values from autoconf (LINUX, LINUXRELEASE, LINUX_OBJ)
to the debian build system to correctly identify kernel sources
(--with-linux) and objects (--with-linux-obj). The 'make debs'
target previously used KERNEL_VERSION, which does not get set
anymore.

Other fixes for building debs with Ubuntu 12.04+:
 1) Add module-assistant to Build-Depends in debian/control
 2) Omit copying lustre-*-orig.tar.gz and lustre-*.diff.gz files
    since this is the upstream source
 3) Change debhelper compatibility level to 7 (10.04+)
 4) Use dh_prep instead of dh_clean -k
 5) avoid non-functional --disable-zerocopy configure option
 6) do not try to install lc_common script that is
    only in server builds

Signed-off-by: Blake Caldwell <blakec@ornl.gov>
Change-Id: I9787bac687d26b03c4d1204347240624bfaced96
Reviewed-on: http://review.whamcloud.com/13129
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Brian J. Murrell <brian.murrell@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>