tree data BUGFIX lyd_owner_module behavior now consistent

It is meant to return the owner module for both
data and opaque nodes. For node modules there
is a new function now.
diff --git a/src/parser_common.c b/src/parser_common.c
index 040318e..bdc8529 100644
--- a/src/parser_common.c
+++ b/src/parser_common.c
@@ -197,7 +197,7 @@
         assert(!iter->schema);
 
         /* get module */
-        mod = lyd_owner_module(iter);
+        mod = lyd_node_module(iter);
         if (!mod) {
             /* unknown module, no schema node */
             schema = NULL;