LU-6210 utils: Use C99 struct initializers in lsnapshot

LU-6210 utils: Use C99 struct initializers in lsnapshot

This patch makes no functional changes.  The long_options struct
initializers in lsnapshot are updated to C99 syntax.  The long
options are 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: Ieccc018218597ade289378fc8666988bf969d924
Reviewed-on: https://review.whamcloud.com/28417
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>