Recalculating index of a virtual Debian repository is calculating the remote repository cache

Description:

When recalculating the index of a virtual Debian repository, in case there is  a remote repository under the virtual repository, the recalculate index process will apply to them as well. In some cases, it will throw exceptions in Artifactory logs.

How to reproduce:

1. Create a virtual Debian repository with a remote virtual repository
2. Prive http://security.debian.org/ as the URL for the remote repository
3. Configure the Debian client as described under the Set Me Up menu and anotate the following to the repository URL 

   buster/updates main contrib non-free

1. Run apt update
2. Recalculate the virtual repository index