Set default vg_options to empty string

library/system/lvg

@@ -105,7 +105,7 @@ def main():
             vg=dict(required=True),
             pvs=dict(type='list'),
             pesize=dict(type='int', default=4),
-            vg_options=dict(),
+            vg_options=dict(default=''),
             state=dict(choices=["absent", "present"], default='present'),
             force=dict(type='bool', default='no'),
         ),