LU-12511 build: avoid building rpm with --disable-modules

LU-12511 build: avoid building rpm with --disable-modules

If you configure lustre with --disable-modules this will prevent
OpenSFS lustre modules from being built but make rpms will fail
since it still expects built modules. Update the lustre.spec
file to not package any modules when --disable-modules is set.

Test-Parameters: trivial
Change-Id: Ide8d80f5b36f819b486a143e56daf494e6a1fe23
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/38369
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Nathaniel Clark <nclark@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>