Make various operation work without a system installation

This makes info, list, remotes, and search work if there is no
system flatpak repo. Before it failed with EPERM.

Closes: #1742
Approved by: alexlarsson
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f