fix(vault): Clean Vault caches before fetching RPC shared secret
Otherwise, RPC secret will be fetched from the DB after migration to Vault
(until `regiond` process is restarted). Since there is no RPC secret in the DB
after migration, region will generate a new secret, preventing clients access.
Now --perf-output-file and --perf-profiling-tag can be specified
when running pytest to control where the output timeing and profiling
data.
I also fixed conftest.py so that pytest can process it in --help.
It had global imports of maasserver, which doesn't work since
django isn't set up when --help runs.
I also made use of pytest_plugins rather than importing all the
fixtures explictly.
It's not needed, and it was somewhat broken. It reverted back to
a savepoint, unless commit_transaction was true. In that case
it simply removed the savepoint. I'm not quite sure what the intent
was there. If it was to simulate a commit, it was in the wrong
place, since it was outside the block that measures the duration.
The transaction is rolled back elsewhere for each tests, so no
need for a custom decorator. The decorator also had logic for
skipping the tests if django wasn't loaded, but I don'