Remote repository creates entry for non-existing packages

If a Conan remote repository is created and a package that doesn't exist is requested from the Conan client, then Artifactory creates the corresponding index.json file for that package and the UI shows an entry for the package.

This happens only in the online mode; if the proxy is offline, no entry is created.

Expected behavior: if the package does not exist in the proxy repository, no entry in the remote one should be created.

How to reproduce:

1. Create a remote conan repository, pointing to any valid proxy: https://conan.bintray.com
2. Add the created remote to the Conan client: "conan remote add <remote> <url>"
3. Install any non-existing-package: "conan install non-existing/version@user/channel -r <remote>"