In case no Renewal/Rebinding times have been provided the server via
DHCP options, we should reset their values on ACK, so that the client
can recalculate the defaults. This is important, as the lease time may
change, so we should recalculate default T1/T2 timeout based on the new
lease time value.
Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>