LU-16586 build: Remove old check for linux_selinux_enabled

LU-16586 build: Remove old check for linux_selinux_enabled

LC_SRC_HAS_LINUX_SELINUX_ENABLED is used and not defined, it
should be removed.

LC_PROG_LINUX_SRC and LC_PROG_LINUX_RESULTS are defined twice,
remove the unused ones.

Fixes: a346cf6cf22 ("LU-13485 kernel: Parallel core configure tests")
Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: I37865c7f7bd6a3f7825084f88295f3fdea8cf920
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/50111
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Petros Koutoupis <petros.koutoupis@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>