DHCP Finite State Machine mishandles renew and rebind.

[BiffoBear]

Issues with current DHCP FSM:

1. Only makes one attempt to obtain a lease and then waits for timeout. UDP is lossy and DHCP standard calls for an exponential fall back retry strategy.
2. When calling the DHCP maintenance routine, the first time it is called after timer T1 has expired, it does not attempt to renew the lease, only sets the FSM state to START. Lease renewal will then be attempted on the next call.
3. If renewal fails (because the original DHCP server is not responding) and timer T2 has expired, FSM does not attempt to rebind by broadcasting the DHCP request, it continues to attempt to renew.
4. Sends messages with broadcast instead of unicast (the DHCP standard to reduce spurious network traffic).