fix insecure manifest inspect with restrictive certs perms

If, for some reason, the certs directory has permissions that are
inaccessible by docker, we should still be able to fetch manifests using
the `insecure` flag.

Since the cli doesn't access the engine's list of insecure registries,
the registry client should make a singleton list of the registry being queried with the
`insecure` flag.

Closes docker#1358

Signed-off-by: Christy Norman <christy@linux.vnet.ibm.com>

cli/registry/client/fetcher.go

@@ -200,7 +200,7 @@ func continueOnError(err error) bool {
 }
 
 func (c *client) iterateEndpoints(ctx context.Context, namedRef reference.Named, each func(context.Context, distribution.Repository, reference.Named) (bool, error)) error {
-	endpoints, err := allEndpoints(namedRef)
+	endpoints, err := allEndpoints(namedRef, c.insecureRegistry)
 	if err != nil {
 		return err
 	}
@@ -262,12 +262,18 @@ func (c *client) iterateEndpoints(ctx context.Context, namedRef reference.Named,
 }
 
 // allEndpoints returns a list of endpoints ordered by priority (v2, https, v1).
-func allEndpoints(namedRef reference.Named) ([]registry.APIEndpoint, error) {
+func allEndpoints(namedRef reference.Named, insecure bool) ([]registry.APIEndpoint, error) {
 	repoInfo, err := registry.ParseRepositoryInfo(namedRef)
 	if err != nil {
 		return nil, err
 	}
-	registryService, err := registry.NewService(registry.ServiceOptions{})
+
+	var serviceOpts registry.ServiceOptions
+	if insecure {
+		logrus.Debugf("allowing insecure registry for: %s", reference.Domain(namedRef))
+		serviceOpts.InsecureRegistries = []string{reference.Domain(namedRef)}
+	}
+	registryService, err := registry.NewService(serviceOpts)
 	if err != nil {
 		return []registry.APIEndpoint{}, err
 	}