Log disk_path instead of path for importer

Merged Zeger-Jan van de Weg requested to merge zj-disk-path-import-error into master

What does this MR do?

Fixes a log line that used Repository#path instead of Repository#disk_path. The #disk_path is relative, but still good enough for the log line. Full paths aren't to be used at GitLab anymore as Gitaly is aware of them.

Does this MR meet the acceptance criteria?

Conformity