dhcp: fix dhclient client killed on no wait

dhcp: fix dhclient client killed on no wait

When a policy dhcp-wait is false the dhcp client is run directly in
background.

But, in most cases, the client won't have the time to find an address
before a check occur.

This is making the client being killed nearly every time.

The obvious solution here is to not check ips differences when no-wait
is asked by the policy.