Add packaging job URL to downstream job url parameters

Previously, the downstream job URL supplied by the user would have
'PACKAGE_BUILD_STATUS' automatically appended to it as a URL parameter, so that
triggered jobs could act on this information. It would also be useful to users
to have the original packaging job URL appended to the downstream job also, so
that any failures are readily accessible from the callback job.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>