use extension of source image on WSL

on WSL, when copying the source image to its local macadam folder
(.local\share\containers\macadam\machine\wsl) macadam was
assuming that the image had .tar.gz format.
However, there is a new WSL distribution format that we have to support
.wsl. This patch adds a check to reuse .wsl extension if sourceUri uses
it.

Signed-off-by: lstocchi <lstocchi@redhat.com>

Author: lstocchi

pkg/imagepullers/noop.go

@@ -39,6 +39,10 @@ func (puller *NoopImagePuller) SetSourceURI(sourcePath string) {
 func imageExtension(vmType define.VMType, sourceURI string) string {
 	switch vmType {
 	case define.WSLVirt:
+		ext := filepath.Ext(sourceURI)
+		if ext == ".wsl" {
+			return ".wsl"
+		}
 		return ".tar.gz"
 	case define.QemuVirt, define.HyperVVirt:
 		return filepath.Ext(sourceURI)