iscsi: Fix IPv6 discovery by stripping Zone ID

This strips off the "%ZONEID" that can be at the end of IPv6
addresses returned by getnameinfo(). Without this, IPv6 discovery
fails because the address has something like "%eth0" appended to it.

Signed of by: Lee Duncan <lduncan@suse.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>