LU-13590 kernel: RHEL 7.9 server support

This patch makes changes to support new RHEL 7.9 release
for Lustre server (kernel 3.10.0-1160.2.1.el7).

Test-Parameters: trivial clientdistro=el7.9 serverdistro=el7.9

Change-Id: I7653091f2bd6a579447edb12045984d2829a8235
Signed-off-by: Jian Yu <yujian@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/40160
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Yang Sheng <ys@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>