Add Linux sysprep for removing /etc/machine-id

This file is created during runtime at early boot and is used to
identify the host in the network.

This resolves #54

image_creator/os_type/linux.py

@@ -333,6 +333,16 @@ class Linux(Unix):
             self.image.g.aug_save()
             self.image.g.aug_close()
 
+    @sysprep('Removing local machine ID configuration file',
+             display="Remove local machine ID configuration file")
+    def _remove_local_machine_id_configuration_file(self):
+        """Remove the /etc/machine-id file if present. This file is used by
+        systemd to uniquelly identify systems and will be created automatically
+        on the next boot if not present."""
+
+        if self.image.g.is_file('/etc/machine-id'):
+            self.image.g.rm('/etc/machine-id')
+
     def _persistent_grub1(self, new_root):
         """Replaces non-persistent device name occurrences with persistent
         ones in GRUB1 configuration files.