main: Ignore 404 error when trying to download _link
With at least obs-api 2.7.4-3co2 and osc 0.167.1-1, when a package is newly branched from another project, it has a pseudo-file named _link in its remote file list but that file cannot actually be downloaded. Ignore the resulting 404 error.
Steps to reproduce the issue that this fixes:
- Have a
foo:bar
project containing a packagehello
- Don't have a
home:you:branches:foo:bar
project osc branch foo:bar hello
osc dput home:you:branches:foo:bar ~/tmp/hello_*_source.changes