Allow to select entries from other sites in entry picker not working

[theresao]

Follow up ticket to https://github.com/presseddigital/linkit/issues/72

After the fix from issue 72 I now have a dropdown with my multisites in the linkit entry picker. When i select an other site in this dropdown, the select options (entries to choose from) do not change. So unfortunately it is still not possible to select entries from other multisites.

It would be great if you could check that again, thank you!