Archive.syncSource doesn't correctly isolate a single copy candidate

[Celso Providelo]

Currently syncSource lookup the copy candidate for the given 'name' and 'version' with:

{{{
source = from_archive.getPublishedSources(
            name=source_name, version=version, exact_match=True)
}}}

The result is not a *single* source, as expected, if the specified source release was published (copied) to more than one suite.

It should always use the first element of the returned ResultSet.

[Celso Providelo (cprov)]

r8298 (db-devel)