LU-7887 lbuild: use "make rpms" for building Lustre RPMs

LU-7887 lbuild: use "make rpms" for building Lustre RPMs

The fact that "make rpms" and lbuild give different results is very
concerning. This patch switch to use common "make rpms" for building
Lustre RPMs in lbuild as well.

Change-Id: Idb27a08f18c4cc45eb658781ecff176628ef22db
Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-on: http://review.whamcloud.com/19037
Tested-by: Jenkins
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>