LU-8126 kernel: new kernel RHEL 6.8 [2.6.32-642.el6]

LU-8126 kernel: new kernel RHEL 6.8 [2.6.32-642.el6]

Changes to support new kernel version in new el6.8 release distro
New kernel-config and target files.
Revised base kernel and ldiskfs patches.
Small adjustments to lbuild and autoconf.

Test-Parameters: clientdistro=el6.8 mdsdistro=el6.8 ossdistro=el6.8

Signed-off-by: Bob Glossman <bob.glossman@intel.com>
Change-Id: I94c0c06f43ca2973133a1dabb0184079290dbc6a
Reviewed-on: http://review.whamcloud.com/20106
Tested-by: Jenkins
Reviewed-by: Minh Diep <minh.diep@intel.com>
Reviewed-by: Yang Sheng <yang.sheng@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>