virt-clone: Don't warn about overwrite of block device

Since nearly every manually specified block path is going to already exist,
don't bother warning about it.

Author: crobinso

virtinst/cli.py

@@ -493,7 +493,7 @@ def disk_prompt(prompt_txt, arg_dict, warn_overwrite=False, prompt_size=True,
         askmsg = _("Do you really want to use this disk (yes or no)")
 
         # Prompt if disk file already exists and preserve mode is not used
-        if warn_overwrite and path_exists:
+        if (path_exists and dev.type == dev.TYPE_FILE and warn_overwrite):
             msg = (_("This will overwrite the existing path '%s'" %
                    dev.path))
             if not prompt_for_yes_or_no(msg, askmsg):