Don't print non bound assignments in the state file

Set bound flag for DHCPv4 and DHCPv6 assignments when the IPv6/IPv4 address
is leased to a client.
This will prevent the printing of leases and hostname/IPv4/IPv6 address
combinations in the state file for for which the IPv4/6 address has not
been assigned.
Also this will fix the printing of assignments which have been declined
by the clients

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>