manila's tempest plugin is branchless and can at
any time add tests for API microversions incompatible
with this stable branch.
We used to configure test API versions via the post test
hook when relying on devstack-gate. However, API version
config makes sense whenever we use devstack and have
tempest enabled. This will help us simplify default
job configuration in the manila-tempest-plugin repository.
Since the API version won't change on a stable branch,
hard-coding the versions (as other micro-versioned services
do in their devstack) doesn't pose any risk of failing
Signed-off-by: Goutham Pacha Ravi <firstname.lastname@example.org>