Candidates from already resolved fragments get ignored if no new hosts are available

org.apache.felix.resolver.Candidates.populateResource(ResolveContext, Resource) gets called for fragments even if they are already resolved so that we can attach them to more hosts as needed.

The issue is that this method will throw a ResolutionException if the fragment cannot attach to any new hosts during the current resolve process. This has the effect of removing any candidate capabilities provided by already resolved fragments.