LU-8537 kernel: kernel update RHEL6.8 [2.6.32-642.4.2.el6]

LU-8537 kernel: kernel update RHEL6.8 [2.6.32-642.4.2.el6]

Update RHEL6.8 kernel to 2.6.32-642.4.2.el6

Test-Parameters: clientdistro=el6.8 mdsdistro=el6.8 ossdistro=el6.8 \
  mdsfilesystemtype=ldiskfs mdtfilesystemtype=ldiskfs \
  ostfilesystemtype=ldiskfs testgroup=review-ldiskfs

Signed-off-by: Bob Glossman <bob.glossman@intel.com>
Change-Id: Idce534b52b69fab8564fbfb6de57cd30d74c84eb
Reviewed-on: http://review.whamcloud.com/22194
Reviewed-by: Minh Diep <minh.diep@intel.com>
Reviewed-by: Yang Sheng <yang.sheng@intel.com>
Tested-by: Jenkins
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>