[FS#829] network.sh incorrectly hardcodes IPv6 address suffix

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - Jo-Philipp Wich (jow-) 

Attached to Project - LEDE Project
Summary - network.sh incorrectly hardcodes IPv6 address suffix 
Task Type - Bug Report
Category - Base system
Status - Assigned
Assigned To - Jo-Philipp Wich
Operating System - All
Severity - Low
Priority - Medium
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - The current implementation of network_get_ipaddr6() and network_get_ipaddrs6() in /lib/function/network.sh incorrectly assumes ":1" as suffix for the local IPv6 address allocated from the delegated prefix.

The effective local address should be taken from the "local-address" field instead.

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=829