Rework in which state to add and not add the server-ip and

Rework in which state to add and not add the server-ip and
requested-ip option as well as setting ciaddr.

This started with joel@ pointing out that their CPE is ignoring
RENEWING and REBINDING requests when ciaddr was not set.

RFC 2131 4.3.6, Table 4 has a good overview, we got a bunch of it
wrong.

Previously the logic for this was all over the place which made it
difficult to reason about, it is now contained in the engine process
in request_dhcp_request() and request_dhcp_discover().

Problem pointed out by, lots of testing and review as well as OK joel@
Additional testing and 50% review benno@