ipset: improve command argument parsing

ipset: improve command argument parsing

The number of comparisons for a matching a command name can be
made smaller by just checking on argv[1].

As an example consider the following 'create' arguments 'hashsize',
'family' and 'timeout'.  When having the command

 create foo hash:ip timeout 60 family inet hashsize 64

it compares without this patch:

 strcmp("timeout", "hashsize")
 strcmp("64", "hashsize")
 strcmp("family", "hashsize")
 strcmp("inet", "hashsize")
 strcmp("hashsize", "hashsize")

It is worse in practice, as 'create' has more arguments than this.

Signed-off-by: Holger Eitzenberger <holger@eitzenberger.org>