networks/utils: Adds networkDHCPv6Release function and associated packet helpers
networks/utils: Adds networkDHCPv6Release function and associated packet helpers

This function sends a manually crafted DHCPv6 release packet to the local dnsmasq server to remove the lease.

Signed-off-by: Thomas Parrott <6b778ce645fb0e3dde76d79eccad490955b1ae74@canonical.com>

hallyn/lxd,hallyn/lxd,mjeanson/lxd,stgraber/lxd,hallyn/lxd,stgraber/lxd,hallyn/lxd,Skarlso/lxd,lxc/lxd,lxc/lxd,lxc/lxd,hallyn/lxd,atxwebs/lxd,Skarlso/lxd,atxwebs/lxd,Skarlso/lxd,lxc/lxd,hallyn/lxd,atxwebs/lxd,atxwebs/lxd,mjeanson/lxd,lxc/lxd,stgraber/lxd,lxc/lxd,Skarlso/lxd,stgraber/lxd,stgraber/lxd,stgraber/lxd,stgraber/lxd,mjeanson/lxd,lxc/lxd