NetworkPkg: Support bracketed IPv6 address during a redirection in iSCSI

NetworkPkg: Support bracketed IPv6 address during a redirection in iSCSI

According to RFC 3720, the TargetAddress provided in a redirection
might be a DNS host name, a dotted-decimal IPv4 address, or a
bracketed IPv6 address. Current ISCSI driver in Networkpkg only
supports dotted-decimal IPv4 address, so we need add IPv6 address
support since it is a combo driver supporting dual stack.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Zhang Lubo <lubo.zhang@intel.com>
Cc: Ye Ting <ting.ye@intel.com>
Cc: Fu Siyuan <siyuan.fu@intel.com>
Cc: Wu Jiaxin <jiaxin.wu@intel.com>
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>