LU-6023 build: fix libselinux support

LU-6023 build: fix libselinux support

Enabling correct libselinux-devel detection by searching for
the same header file in autoconf that is used in code.

Link mount_osd_ldiskfs.so with -lselinux.

Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Change-Id: I085e91464a263b6d1b1be13971e54dfc80a4e347
Reviewed-on: http://review.whamcloud.com/13030
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>