Fix generating manifest when install hybrid package

Fix generating manifest when install hybrid package

Currently, wgt-backend generate manifest file using manifest_x which is
parsed by manifest parser. This data contains only the parser knows.
However, the manifest file for native packages have many element which
are not parsed manifest parser but parsed by plugin parsers.
So the manifest generated by wgt-backend loses some elements.

This patch will make the manifest have elements as it was before.
StepGenerateXml from hybrid installer will merge original native
manifest into generated widget manifest(config.xml).

Change-Id: Iea0a68c3b695243248469f0794f62f7bec4fa757
Signed-off-by: Sangyoon Jang <s89.jang@samsung.com>