LU-9215 build: Re-add the lustre-devel package

Traditonally on rpm systems a special devel package exist that
contains userland headers and symlinks for the libraries. This
patch creates such a package.

The introduction of this new package changes the dependency
of lustre-test packages since the user land headers are tested
to make sure they compile for user land applications. Update
the dpk package as well.

Lastly we add pkg-config support to Lustre as well. This means
that if do configure --prefix=special_place it will not break
external applications if they use pkg-config.

Change-Id: I3e856d85239d1712e21f7ecc633d9fae569238e6
Test-Parameters: trivial
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/40728
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Nathaniel Clark <nclark@whamcloud.com>
Reviewed-by: Alexey Lyashkov <alexey.lyashkov@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>