Update c/image for https://github.com/containers/image/pull/912

This is an unreleased version of c/image, but it is important to
to have the test added in in the next commit enforcing as soon as
possible.

> go get github.com/containers/image/v5@HEAD
> make vendor

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

vendor/github.com/containers/storage/store.go

@@ -3397,7 +3397,7 @@ func copyStringInterfaceMap(m map[string]interface{}) map[string]interface{} {
 }
 
 // defaultConfigFile path to the system wide storage.conf file
-const defaultConfigFile = "/etc/containers/storage.conf"
+var defaultConfigFile = "/etc/containers/storage.conf"
 
 // AutoUserNsMinSize is the minimum size for automatically created user namespaces
 const AutoUserNsMinSize = 1024
@@ -3409,6 +3409,11 @@ const AutoUserNsMaxSize = 65536
 // creating a user namespace.
 const RootAutoUserNsUser = "containers"
 
+// SetDefaultConfigFilePath sets the default configuration to the specified path
+func SetDefaultConfigFilePath(path string) {
+	defaultConfigFile = path
+}
+
 // DefaultConfigFile returns the path to the storage config file used
 func DefaultConfigFile(rootless bool) (string, error) {
 	if rootless {