qemu-iotests: Add TestRepairQuorum to 041 to test drive-mirror node-name mode.

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>