Add two functions required by ipamapi "contract" but not actually used

plugin/ipam/driver.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"net"
 
+	"github.com/docker/libnetwork/discoverapi"
 	"github.com/docker/libnetwork/ipamapi"
 	"github.com/docker/libnetwork/netlabel"
 	godocker "github.com/fsouza/go-dockerclient"
@@ -67,3 +68,13 @@ func (i *ipam) ReleaseAddress(poolID string, address net.IP) error {
 	Log.Debugln("ReleaseAddress", poolID, address)
 	return i.weave.ReleaseIP(address.String())
 }
+
+// Functions required by ipamapi "contract" but not actually used.
+
+func (i *ipam) DiscoverNew(discoverapi.DiscoveryType, interface{}) error {
+	return nil
+}
+
+func (i *ipam) DiscoverDelete(discoverapi.DiscoveryType, interface{}) error {
+	return nil
+}