Use the IANA assigned IPv6 multicast addresses for "All OCF Nodes".

Use the IANA assigned IPv6 multicast addresses for "All OCF Nodes".

In order to avoid processing incompatible messages with CoAP application
syntax in constrained devices, OCF has registered its own IPv6 multicast
address. This patch changes the IPv6 multicast address used for
discovery and group messages from “All CoAP Nodes” to “All OCF Nodes”.
See
http://www.iana.org/assignments/ipv6-multicast-addresses/ipv6-multicast-addresses.xhtml

Change-Id: I6ff4069bde6bdcfc40bd5aa216108f2de6a18ed5
Signed-off-by: Stephane Lejeune <stlejeun@cisco.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/9289
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Jon A. Cruz <jon@joncruz.org>