Fix logic of safe mode guard on reformat.

A type of None means no formatting. An exception is when there is a
blkid-reported type that blivet doesn't have special handling for,
in which case type will be None but the name attribute will reflect
the type reported by blkid. In this special case we treat the
formatting as though it had a non-None type.

library/blivet.py

@@ -218,7 +218,7 @@ def _reformat(self):
         if self._device.format.type == fmt.type:
             return
 
-        if safe_mode and self._device.format.type is None and self._device.format.name != get_format(None).name:
+        if safe_mode and self._device.format.type is not None or self._device.format.name != get_format(None).name:
             raise BlivetAnsibleError("cannot remove existing formatting on volume '%s' in safe mode" % self._volume['name'])
 
         if self._device.format.status: