Steps to reproduce:
1) Create npm local, remote and virtual repos
2) Install some packages using npm
3) Set the npm-remote repo to "offline"
4) Go to the virtual and recalculate index
Result:
2016-01-27 20:09:56,491 [http-nio-8081-exec-44] [INFO ] (o.a.u.r.s.a.b.t.a.RecalculateIndexService:28) - Recalculating index for repository npm-virtual scheduled to run
2016-01-27 20:10:51,930 [http-nio-8081-exec-52] [INFO ] (o.a.a.n.r.m.NpmPackageMetadataMerger:143) - Fetching external dependencies for 'directory-colorfy' from 'npm-remote'
Should not attempt to retrieve metadata from a remote that is offline.