#96 DHCP discovery does not use all interfaces

[Alan]

OpenSLP DA discovery by multicast uses an interface list and attempts to perform discovery over all specified interfaces.

DA discovery by DHCP only attempts a single interface, which may not be the interface on which a DHCP server is responding and/or may not be the network on which DHCP is providing SLP configuration information.

DHCP-based discovery needs to issue a DHCP Inform to all interfaces OpenSLP has been configured/allowed to use, more similar to the multicast discovery approach.