NetconfAccess: switch to <get-data> for getItems

Advantages of using <get-data>:
- it makes it more similar to SysrepoAccess because both use NMDA
datastores
- get-data doesn't suffer from a Netopeer2 bug. More info here:
https://github.com/sysrepo/sysrepo/issues/2231#issuecomment-756277207

Disadvantages:
- the remote server might not support it

Change-Id: Ibecacf6f992b3f2e6c4087aac2e84812e28e44cf
diff --git a/src/netconf_access.cpp b/src/netconf_access.cpp
index 4ed29ae..64e2f76 100644
--- a/src/netconf_access.cpp
+++ b/src/netconf_access.cpp
@@ -19,7 +19,7 @@
 DatastoreAccess::Tree NetconfAccess::getItems(const std::string& path) const
 {
     Tree res;
-    auto config = m_session->get((path != "/") ? std::optional{path} : std::nullopt);
+    auto config = m_session->getData(libnetconf::NmdaDatastore::Operational, (path != "/") ? std::optional{path} : std::nullopt);
 
     if (config) {
         lyNodesToTree(res, config->tree_for());