Revert "remote-bzr: split marks file"

This reverts commit f862c0f8ca47d75dd535d99ac257cd3b6427e80a.

Works fine for fetching, but not pushing. For proper pushing we need
per-repo marks. A proper solution will take time, if at all possible.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>