* Stricter handling of multi-namespace handling

* This occurs in cases where there are more than one XML namespaces in a config tree, such as `augment`:ed trees.
  * Affects all parts of the system, including datastore, backend, restconf and cli.
* Invalid api-path syntax (eg non-matching yang) error changed from 412 operation-failed to 400 Bad request invalid-value, or unknown-element.

apps/backend/backend_commit.c

@@ -195,10 +195,12 @@ startup_common(clicon_handle       h,
 	goto ok;
     }
     if (msd){
+	/* Here xt is old syntax */
 	if ((ret = clixon_module_upgrade(h, xt, msd, cbret)) < 0)
 	    goto done;
 	if (ret == 0)
 	    goto fail;
+	/* Here xt is new syntax */
     }
     if ((yspec = clicon_dbspec_yang(h)) == NULL){
 	clicon_err(OE_YANG, 0, "Yang spec not set");