src/bin/dhcp6/dhcp6_srv.h
src/bin/dhcp6/dhcp6_srv.cc

replaced parameters subnet and duid with a single paramter for context in
several methods:
    assignIA_NA()
    assignIA_PD()
    extendIA_NA()
    extendIA_PD()
    extendLeases()

appendRequestedVendorOptions() - added context parameter, removed
redundant call to selectSubnet

processClientFqdn() -
    Now sets the hostname value in the context in addition to processing FQDN.
    This centralizes the logic to handle both, since they are tightly coupled
    and can be influenced by a host reservation.

    Note that when the host name from the reservation is being used in place
    of the client FQDN, the qualyfing suffix is always appended to the hostname.
    This is consistent with the DHCPv4 behavior.