DHCP4 client process replies when renewing lease

DHCP4 client process replies when renewing lease

When a DHCP client is in the bound state, it wakes up
halfway through it's lease (by default) to try and renew
the lease. The ip4-dhcp-client-detect is not enabled as
a feature at this point, so replies sent from the DHCP
server do not get applied to the lease. Eventually the
lease expires, the address is removed from the interface,
a new discovery is performed and the same address is added
back to the interface.

Before sending a request to renew in the bound state, enable
the feature to process the reply.

Change-Id: I95332ee0596f47df6f3c8bf8e3f0698dde9a1fc5
Signed-off-by: Matthew Smith <mgsmith@netgate.com>