test/osd/RadosModel: assure that tid seq is contiguous

test/osd/RadosModel: assure that tid seq is contiguous

before this change:

4:  finishing write tid 1 to gen81094472-1
4:  finishing write tid 2 to gen81094472-1
4:  finishing write tid 3 to gen81094472-1
4:  finishing write tid 5 to gen81094472-1
4:  finishing write tid 6 to gen81094472-1

after this change:

1:  finishing write tid 1 to gen81117124-1
1:  finishing write tid 2 to gen81117124-1
1:  finishing write tid 3 to gen81117124-1
1:  finishing write tid 4 to gen81117124-1
1:  finishing write tid 5 to gen81117124-1

more pleasant when reading the logging messages.

Signed-off-by: Kefu Chai <kchai@redhat.com>