Fix NetconfAccess::deletePresenceContainer

This method had the same problem as deleteListInstance.

Bug: https://tree.taiga.io/project/jktjkt-netconf-cli/issue/153
Change-Id: I84d6c3323a69156c54c1159b153cdce8a22941c7
diff --git a/tests/example-schema.yang b/tests/example-schema.yang
index a7ff3d8..cbd5d8d 100644
--- a/tests/example-schema.yang
+++ b/tests/example-schema.yang
@@ -6,6 +6,12 @@
         prefix other;
     }
 
+    container inventory {
+        container stuff {
+            presence true;
+        }
+    }
+
     leaf leafUInt8 {
         type uint8;
     }