os-networks extension

This commit adds the os-networks extention. This can be used to view
details about the nova-network-based networks that a tenant has access
to.
diff --git a/acceptance/openstack/compute/v2/network_test.go b/acceptance/openstack/compute/v2/network_test.go
new file mode 100644
index 0000000..7ebe7ec
--- /dev/null
+++ b/acceptance/openstack/compute/v2/network_test.go
@@ -0,0 +1,78 @@
+// +build acceptance compute servers
+
+package v2
+
+import (
+	"os"
+	"testing"
+
+	"github.com/rackspace/gophercloud"
+	"github.com/rackspace/gophercloud/openstack/compute/v2/extensions/networks"
+	"github.com/rackspace/gophercloud/openstack/compute/v2/servers"
+	th "github.com/rackspace/gophercloud/testhelper"
+)
+
+func getNetworkIDFromNetworkExtension(t *testing.T, client *gophercloud.ServiceClient, networkName string) (string, error) {
+	allPages, err := networks.List(client).AllPages()
+	if err != nil {
+		t.Fatalf("Unable to list networks: %v", err)
+	}
+
+	networkList, err := networks.ExtractNetworks(allPages)
+	if err != nil {
+		t.Fatalf("Unable to list networks: %v", err)
+	}
+
+	networkID := ""
+	for _, network := range networkList {
+		t.Logf("Network: %v", network)
+		if network.Label == networkName {
+			networkID = network.ID
+		}
+	}
+
+	t.Logf("Found network ID for %s: %s\n", networkName, networkID)
+
+	return networkID, nil
+}
+
+func TestNetworks(t *testing.T) {
+	networkName := os.Getenv("OS_NETWORK_NAME")
+	if networkName == "" {
+		t.Fatalf("OS_NETWORK_NAME must be set")
+	}
+
+	choices, err := ComputeChoicesFromEnv()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	client, err := newClient()
+	if err != nil {
+		t.Fatalf("Unable to create a compute client: %v", err)
+	}
+
+	networkID, err := getNetworkIDFromNetworkExtension(t, client, networkName)
+	if err != nil {
+		t.Fatalf("Unable to get network ID: %v", err)
+	}
+
+	// createNetworkServer is defined in tenantnetworks_test.go
+	server, err := createNetworkServer(t, client, choices, networkID)
+	if err != nil {
+		t.Fatalf("Unable to create server: %v", err)
+	}
+	defer func() {
+		servers.Delete(client, server.ID)
+		t.Logf("Server deleted.")
+	}()
+
+	if err = waitForStatus(client, server, "ACTIVE"); err != nil {
+		t.Fatalf("Unable to wait for server: %v", err)
+	}
+
+	allPages, err := networks.List(client).AllPages()
+	allNetworks, err := networks.ExtractNetworks(allPages)
+	th.AssertNoErr(t, err)
+	t.Logf("Retrieved all %d networks: %+v", len(allNetworks), allNetworks)
+}