Validate listener's IP address before adding it

[gbregman]

When we run a "listener add" command using an invalid IP address the error code we get back from SPDK is a generic one "invalid parameters". We can't tell what was the actual problem. We can validate the IP address in the gateway. Iterating the available ethernet interfaces and checking that the IP address we got is one of the ones on that list. We should allow the user to disable this validation by setting a flag in the configuration.