Vivid raid1 smoke test fail to mount root partition

[Diogo Matsubara]

Vivid's raid1 smoke test[1] fails with the following error:

    FAIL: testRootMount (__main__.RAID1Test)
    ----------------------------------------------------------------------
    Traceback (most recent call last):
      File "test.py", line 39, in testRootMount
        "/ partition not in raid device")
    AssertionError: / partition not in raid device

[1] http://d-jenkins.ubuntu-ci:8080/view/Vivid/view/Smoke%20Testing/job/vivid-server-i386-smoke-raid1/

[Diogo Matsubara (matsubara)]

I ran into a weird issue debugging this test failure. I added the following change http://pastebin.ubuntu.com/10961577/ to the test case, so I could see what the `df -h` output was, then kicked another test run here: http://d-jenkins.ubuntu-ci:8080/view/Vivid/view/Smoke%20Testing/job/vivid-server-amd64-smoke-raid1/140/artifact/utah-36792-vivid-server-amd64_raid1.run_2015-05-01_11-05-09.yaml/*view*/

The output from my debug command shows the root file systems is mounted to /dev/md0 which is what the test case expects but when the subsequent `df -h /` command runs the output returned is different and shows the device by uuid: /dev/disk/by-uuid/28e0ef45-c224-40b5-a0e7-49fde0bb5528 which obviously won't match the test expectation. So what is confusing is why I get different outputs from df depending on what parameters I pass to the command.