Use true and false instead of yes and no for boolean values

Story: 2010586
Task: 47380
Change-Id: I1b88aa925d823d74b2d012153dfe26d35c93dfd5

plugins/modules/volume_snapshot.py

@@ -22,7 +22,7 @@ options:
        - Allows or disallows snapshot of a volume to be created,
          when the volume is attached to an instance.
     type: bool
-    default: 'no'
+    default: 'false'
   name:
     description:
       - Name of the snapshot