LU-506 tests: check lustre.conf for modprobe

The newer userspace modprobe requires that the /etc/modprobe.d/
files end in ".conf", so that there is no confusion between config
files that are supposed to be parsed, and files that are left
after editing (e.g. lustre.conf.orig or lustre.conf~).

Add a check for /etc/modprobe.d/lustre.conf to get lnet module
parameters during testing.

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ie408f5334b2570f13e225038488df06ff7b524c4
Reviewed-on: http://review.whamcloud.com/1877
Tested-by: Hudson
Reviewed-by: Brian J. Murrell <brian@whamcloud.com>
Reviewed-by: Yu Jian <yujian@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>