RDKB-38526: Misleading value for "Delegated Prefix" attribute on GUI.
RDKB-38526: Misleading value for "Delegated Prefix" attribute on GUI.

Reason for change: "Device.IP.Interface.1.IPv6Prefix.1.Prefix" data model value
                    is taken from "tr_erouter0_dhcpv6_client_v6pref" sysevent.
		    Currently, it is set to "/64" in the WAN manager and PAM component.
	            So, changing the sysevent to the received wan prefix to
		    display correct results in the webUI.

Test Procedure:
1. Correct value wan prefix to be displayed in webUI.
2. Checked zebra process and its configurations.
3. Checked dibbler server process and its confirations.

Risks: Low

Signed-off-by: Abhishek Sivappa <7e3eb8981bec8c18a3ba1b7080ab5e6852298347@sky.uk>
(cherry picked from commit 041fdd561951036cf7a761746ad955c663607fd3)
Change-Id: I6bb6b39039e6ce336e337e8c800f923f5ca84d6c

rdkcmf/rdkb-CcspPandM,rdkcmf/rdkb-CcspPandM,rdkcmf/rdkb-CcspPandM