ipset: propose rewording in manpage

ipset: propose rewording in manpage

I have prepared the patch which refers to
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=780336,
reported and proposed by H. Renault <hr@herverenault.fr>.

man ipset reads:

    del SETNAME DEL-ENTRY [ DEL-OPTIONS ]
        Delete an entry from a set. If the -exist option is specified,
        ipset ignores if the entry does not added to  (already expired
        from)  the set.

Proposed rewording:

        Delete an entry from a set. If the -exist option is specified
        and the entry is not in the set (maybe already expired), then
        the command is ignored.

Signed-off-by: Neutron Soutmun <neo.neutron@gmail.com>
Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>