Port the legacy legacy-tempest-dsvm-multibackend-matrix job to the
native Zuul v3 syntax, and rename it following the guidelines
(cinder-multibackend-matrix-migration).
This job tests the migration between two different backends
specified through the volume.backend_names configuration
key in tempest.conf.
Now the job leverages the existing zuul code, namely the
run-tempest role, which is called multiple times with all
the possible combinations of the 3 tested backends
(lvm, ceph, nfs) where the source and the destination differ.
The final JUnitXML output summarizes the test results
for each of the tested combinations.
Change-Id: I34e7e48ee63c4c269f82ae178a7118ed402cad6d
1c0c25babb