qemu-iotests: Add TestRepairQuorum to 041 to test drive-mirror node-name mode. The to-replace-node-name is designed to allow repairing a broken Quorum file. This patch introduces a new class TestRepairQuorum testing that the feature works. Some further work will be done on QEMU to improve the robustness of the tests. Signed-off-by: Benoit Canet <benoit@irqsave.net> Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>