Fix path namespace resolution
If a path is defined in terms of a submodule-local import,
SchemaContextUtil.findDataSchemaNode() breaks down because
it's reparse attempt fails to find the import in the actual
module.
SchemaContextUtil is providing findDataTreeSchemaNode() which
works properly on parsed PathExpression, use that instead.
JIRA: MDSAL-499
Change-Id: Ifa8a8958d7118d851d27fcc2c70c6d8382e3e3c0
Signed-off-by: miroslav.kovac <miroslav.kovac@pantheon.tech>
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>