plugins: correctly output build version, cosmetic cleanups

Now that libcni has the ability to print a version message, plumb it
through correctly.

While we're at it,
- fix import paths
- run gofmt
- add some more comments to sample
- add container runtime swappability for release

plugins/ipam/dhcp/main.go

@@ -27,6 +27,7 @@ import (
 	"github.com/containernetworking/cni/pkg/types"
 	"github.com/containernetworking/cni/pkg/types/current"
 	"github.com/containernetworking/cni/pkg/version"
+	bv "github.com/containernetworking/plugins/pkg/utils/buildversion"
 )
 
 const defaultSocketPath = "/run/cni/dhcp.sock"
@@ -51,8 +52,7 @@ func main() {
 			os.Exit(1)
 		}
 	} else {
-		// TODO: implement plugin version
-		skel.PluginMain(cmdAdd, cmdCheck, cmdDel, version.All, "TODO")
+		skel.PluginMain(cmdAdd, cmdCheck, cmdDel, version.All, bv.BuildString("dhcp"))
 	}
 }
 

plugins/ipam/dhcp/options.go

@@ -98,7 +98,7 @@ func parseCIDRRoutes(opts dhcp4.Options) []*types.Route {
 			}
 			routes = append(routes, rt)
 
-			opt = opt[octets+5 : len(opt)]
+			opt = opt[octets+5:]
 		}
 	}
 	return routes

plugins/ipam/dhcp/options_test.go

@@ -24,14 +24,14 @@ import (
 
 func validateRoutes(t *testing.T, routes []*types.Route) {
 	expected := []*types.Route{
-		&types.Route{
+		{
 			Dst: net.IPNet{
 				IP:   net.IPv4(10, 0, 0, 0),
 				Mask: net.CIDRMask(8, 32),
 			},
 			GW: net.IPv4(10, 1, 2, 3),
 		},
-		&types.Route{
+		{
 			Dst: net.IPNet{
 				IP:   net.IPv4(192, 168, 1, 0),
 				Mask: net.CIDRMask(24, 32),