Use a hard-coded project_id in racy cinder.tests.unit.test_volume tests

Use a hard-coded project_id in racy cinder.tests.unit.test_volume tests

Since concurrent unit test runs have been turned on with ostestr there
are races with the notifications causing the assertions in
test_volume.py tests to fail.

A few attempts have been made at writing an elastic-recheck query to
identify the failures but they are too generic, e.g. querying for
"fake_notifier.NOTIFICATIONS" or "MismatchError 0 != ", which could hit
on anything that fails with those, e.g. anything that uses
"self.assertEqual(0, " in the code could hit that kind of query - and we
want to avoid those types of queries running against changes in the
check queue since they could mask legitimate test failures.

So we add something unique in these tests to identify them from other
test failures in Cinder by using a hard-coded uuid for the project_id so
that if we have an assertion failure with notifications, the
notification payload is dumped (due to commit
4bbe1c87e26150c62e1dc8a2a5b8979896c1ddd9) and we can query on the
assertion failure plus the hard-coded project_id used only in these
tests.

Related-Bug: #1412513

Change-Id: I57f597a1bb2fdfeb24c17ac9020cc96f1ebf3fdd