restapi: provide full_version in product_info

Frontend uses ProductRPMVersion from vdc_options to show Engine version.
This patch will include a new element called full_version into ProductInfo xsd schema,
which will provide to users the same version info from Frontend.

Change-Id: Ie5c03460ef1af943278ab6f5171c042afdf4d392
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=905398
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>