LU-9148 kernel: kernel update RHEL6.8 [2.6.32-642.15.1.el6]

LU-9148 kernel: kernel update RHEL6.8 [2.6.32-642.15.1.el6]

Update RHEL6.8 kernel to 2.6.32-642.15.1.el6

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

Signed-off-by: Bob Glossman <bob.glossman@intel.com>
Change-Id: Iaac7b99246b9e9d3204c3545aaf0b9d2fd8d3185
Reviewed-on: https://review.whamcloud.com/25633
Tested-by: Jenkins
Reviewed-by: Minh Diep <minh.diep@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Nunez <james.a.nunez@intel.com>
Reviewed-by: Yang Sheng <yang.sheng@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>