LU-11720 spec: srpm should be free of kernel requiements

LU-11720 spec: srpm should be free of kernel requiements

This moves the fix for LU-9731 into spec file and out of lbuild.
This lets "make rpms" benefit from the fix.
This also prevents the srpm from being incorrectly locked to the
kernel present when lbuild was used to create it (via
kmp-lustre.preamble).

Test-Parameters: trivial

Lustre-change: https://review.whamcloud.com/33771
Lustre-commit: 3c280a95736a884bc2f36dad674505f1d5b00982

Signed-off-by: Nathaniel Clark <nclark@whamcloud.com>
Change-Id: I15f61c0e37182c0efbea3566d43b1e89f180d3e5
Tested-by: Jenkins
Reviewed-by: Gu Zheng <gzheng@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Signed-off-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/34268
Tested-by: Maloo <maloo@whamcloud.com>