depchase: Fix get_rpms_for_srpms lookup mapping
    
    The logic here is flawed, adding the arbitrarily first returned package
    name from libsolv to the sources list, when we should be adding the
    package name we actually compared against.
    
    The one caller is used for populating the RPM list for the bootstrap
    module: previously the code thought there was only around 1700 RPMs
    in bootstrap, after this fix it's closer to 12000