Always pull images by default

The behaviour prior to this patch caused some confusion for
users since they expected a behaviour like Swarm / Kubernetes
which always pulls images by default, even if cached. I've tested
the change and it is working as expected. By default images are
always pulled upon deployment.

To revert to the prior behaviour, simply add to faasd up:
--pull-policy=IfNotPresent

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

pkg/supervisor.go

@@ -8,13 +8,13 @@ import (
 	"os"
 	"path"
 
-	"github.com/openfaas/faasd/pkg/cninetwork"
-	"github.com/openfaas/faasd/pkg/service"
 	"github.com/containerd/containerd"
 	"github.com/containerd/containerd/cio"
 	"github.com/containerd/containerd/containers"
 	"github.com/containerd/containerd/oci"
 	gocni "github.com/containerd/go-cni"
+	"github.com/openfaas/faasd/pkg/cninetwork"
+	"github.com/openfaas/faasd/pkg/service"
 
 	"github.com/containerd/containerd/namespaces"
 	"github.com/opencontainers/runtime-spec/specs-go"
@@ -24,7 +24,8 @@ const (
 	defaultSnapshotter         = "overlayfs"
 	workingDirectoryPermission = 0644
 	// faasdNamespace is the containerd namespace services are created
-	faasdNamespace = "default"
+	faasdNamespace         = "default"
+	faasServicesPullAlways = false
 )
 
 type Service struct {
@@ -88,7 +89,7 @@ func (s *Supervisor) Start(svcs []Service) error {
 	for _, svc := range svcs {
 		fmt.Printf("Preparing: %s with image: %s\n", svc.Name, svc.Image)
 
-		img, err := service.PrepareImage(ctx, s.client, svc.Image, defaultSnapshotter)
+		img, err := service.PrepareImage(ctx, s.client, svc.Image, defaultSnapshotter, faasServicesPullAlways)
 		if err != nil {
 			return err
 		}