LU-17029 lustre.spec.in: match rpm macro openEuler for openEuler Linux

LU-17029 lustre.spec.in: match rpm macro openEuler for openEuler Linux

So that it can handle openEuler derived OSes, because different
derived OS has different vendor name, like KylinOS's vendor name
is Kylin.

Change-Id: I12ceda5bf9d1f17a75d4adddbad292fd1ae9967b
Test-Parameters: trivial
Signed-off-by: Xinliang Liu <xinliang.liu@linaro.org>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/51954
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>