Add tests for dm-writeboost

dm-writeboost is a caching driver like dm-cache, bcache and enhance-io.
This patch introduces the minimum stack and tests for writeboost driver.

Now,
`dmtest list --suite writeboost` shows

writeboost
  WriteboostTests
    fio_cache
    fio_database_funtime
    fio_sub_volume
Merge pull request #3 from akiradeveloper/feature/add-writeboost-test

Add tests for dm-writeboost
Fix path (fio config and the output file)

Add AP and LP in Utils module
which converts given path to Absolute (from the caller's initial
location) path and to lib/dmtest/${path} respectively.

Writeboost runs its three tests without failure now.
Also, fixed the things for dm-cache and bcache.
Merge pull request #5 from akiradeveloper/feature/fix-fio-path-to-run-writeboost-test

Fix path (fio config and the output file)
[PoolStatus] parse the options correctly

They used to have a field indicating how many options were present.
Now gone, presumably removed on the way upstream by a fiddler.
[thin-provisioning] Improve test_exhausting_metadata_space_causes_fail_mode

- Now checks the pool mode in the status.
- Reduce the metadata space (sometimes there was enough depending on commits)
- Remove old code that was dumping metadata due to a thin_check bug (since fixed)
- Use a variant of ProcessControl.run that allows the dd process to fail
Merge branch 'master' of github.com:jthornber/device-mapper-test-suite
CacheStack#activate and activate_support_devs now pass on the value returned by their block
[cache] refactor ResizeTests
Add some cache warming tests that use the new mq tunables
thin throughput tests
[thin] forgot oflags=direct in the ThroughputTests
[thin] Update Throughput tests
[thin] Add a linear throughput test to ThroughputTests for baseline comparison
[cache] MetadataScalingTests
[cache] MetadataScalingTests now assert against expected results
Merge with Mike
Add EraTarget
Era creation and linear properties tests
prepare_era_then_check_after_reload