CLI: Allow deleting leaf nodes

This is allowed for YANG datastores; the semantics is that a default
value appears there if defined, otherwise the node just doesn't return
any data when requested.

Change-Id: I9e39ade3e08720b116a674650a02399cbffd854e
diff --git a/src/grammars.hpp b/src/grammars.hpp
index 9f0baf2..3cc74f2 100644
--- a/src/grammars.hpp
+++ b/src/grammars.hpp
@@ -57,7 +57,7 @@
     create_::name >> space_separator > (presenceContainerPath | listInstancePath | leafListElementPath);
 
 auto const delete_rule_def =
-    delete_::name >> space_separator > (presenceContainerPath | listInstancePath | leafListElementPath);
+    delete_::name >> space_separator > (presenceContainerPath | listInstancePath | leafListElementPath | writableLeafPath);
 
 auto const get_def =
     get_::name >> -(space_separator >> ((dataPathListEnd | dataPath) | (module >> "*")));