Fuzzy finder: filenames are incorrectly cached for old repository when switching to a new repository

Created by: olafurpg

Reproduction

• Open https://sourcegraph.com/github.com/sourcegraph/sourcegraph
• Trigger Cmd+K, see sourcegraph/sourcegraph files as expected
• Search for lsif-java, open the lsif-java repo
• Trigger Cmd+K, the sourcegraph/sourcegraph files are shown instead of sourcegraph/lsif-java files