GVFS mount shown as empty after disconnect

Hi,

there's more GVFS issues open, but I haven't found this particular one yet (I think).

When a GVFS mount disconnects (e.g. timeout after suspend), it is shown as empty. Thunar will not automatically reconnect to previously visited locations, but will reconnect to new locations on the same host. It seems cache invalidation is broken, leading Thunar to assume disconnected drives are merely empty.

Repro:

1. Connect to sftp://server
2. Browse to sftp://server/foo/bar
3. -> Everything working fine so far
4. Suspend the device for a few minutes to force the SFTP connection to time out
5. Browse to sftp://server/foo/bar
6. -> Location is either shown as empty or non-existent
7. Browse to sftp://server/foo
8. -> Location is either shown as empty or non-existent
9. Browse to sftp://server
10. -> Location is either shown as empty or non-existent
11. Browse to sftp://server/baz/test
12. -> Thunar finally noticed that SFTP is not even connected and offers to re-establish the connection
13. -> Now sftp://server/foo/bar and the others also start working again

Thanks!