LU-18109 utils: adding nodemap offset capability

LU-18109 utils: adding nodemap offset capability

nodemap offset: the ability to add an offset range to nodemaps.
When an offset is defined, idmaps can only be set inside of their
given range. This is defined as:

lctl nodemap_add_offset --name nodemap --offset 100000 --limit 99999

And removed as:

lctl nodemap_del_offset --name nodemap

Test sanity-sec 27ab is added to exercise this new feature.

Signed-off-by: Maximilian Dilger <mdilger@whamcloud.com>
Change-Id: Iba2116d21bc7de1ba03111b0313427301e4b0b50
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/55943
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>