LU-6171 kernel: kernel update [RHEL7 3.10.0-123.20.1.el7]

LU-6171 kernel: kernel update [RHEL7 3.10.0-123.20.1.el7]

update RHEL7 kernel to 3.10.0-123.20.1.el7

Test-Parameters: clientdistro=el7 mdsfilesystemtype=ldiskfs\
        mdtfilesystemtype=ldiskfs ostfilesystemtype=ldiskfs

Signed-off-by: Bob Glossman <bob.glossman@intel.com>
Change-Id: Ieb1e8a2bb4cd86268721af91dd15d2c5bc69d0bf
Reviewed-on: http://review.whamcloud.com/13570
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Yang Sheng <yang.sheng@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>