LU-6210 utils: Use C99 initializer in jt_nodemap_add_idmap()

LU-6210 utils: Use C99 initializer in jt_nodemap_add_idmap()

This patch makes no functional changes.  The long_options struct
initializer in jt_nodemap_add_idmap() is updated to C99 syntax.
It is renamed to long_opts for consistency.

C89 positional initializers require values to be placed in the
correct order. This will cause errors if the fields of the struct
definition are reordered or fields are added or removed. C99 named
initializers avoid this problem, and also automatically clear any
values that are not explicitly set.

Test-Parameters: trivial
Signed-off-by: Steve Guminski <stephenx.guminski@intel.com>
Change-Id: Iafeb7e76a943d8f8118623c532da1e8e2880aba2
Reviewed-on: https://review.whamcloud.com/27890
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>