Use external placement in functional tests

Adjust the fixtures used by the functional tests so they
use placement database and web fixtures defined by placement
code. To avoid making redundant changes, the solely placement-
related unit and functional tests are removed, but the placement
code itself is not (yet).

openstack-placement is required by the functional tests. It is not
added to test-requirements as we do not want unit tests to depend
on placement in any way, and we enforce this by not having placement
in the test env.

The concept of tox-siblings is used to ensure that the
placement requirement will be satisfied correctly if there is a
depends-on. To make this happen, the functional jobs defined in
.zuul.yaml are updated to require openstack/placement.

tox.ini has to be updated to use a envdir that is the same
name as job. Otherwise the tox siblings role in ansible cannot work.

The handling of the placement fixtures is moved out of nova/test.py
into the functional tests that actually use it because we do not
want unit tests (which get the base test class out of test.py) to
have anything to do with placement. This requires adjusting some
test files to use absolute import.

Similarly, a test of the comparison function for the api samples tests
is moved into functional, because it depends on placement functionality,

TestUpgradeCheckResourceProviders in unit.cmd.test_status is moved into
a new test file: nova/tests/functional/test_nova_status.py. This is done
because it requires the PlacementFixture, which is only available to
functional tests. A MonkeyPatch is required in the test to make sure that
the right context managers are used at the right time in the command
itself (otherwise some tables do no exist). In the test itself, to avoid
speaking directly to the placement database, which would require
manipulating the RequestContext objects, resource providers are now
created over the API.

Co-Authored-By: Balazs Gibizer <balazs.gibizer@ericsson.com>
Change-Id: Idaed39629095f86d24a54334c699a26c218c6593

tox.ini

@@ -73,9 +73,23 @@ commands =
 [testenv:functional]
 # TODO(melwitt): This can be removed when functional tests are gating with
 # python 3.x
+# NOTE(cdent): For a while, we shared functional virtualenvs with the unit
+# tests, to save some time. However, this conflicts with tox siblings in zuul,
+# and we need siblings to make testing against master of other projects work.
 basepython = python2.7
-envdir = {toxworkdir}/py27
 setenv = {[testenv]setenv}
+# As nova functional tests import the PlacementFixture from the placement
+# repository these tests are, by default, set up to run with latest master from
+# the placement repo. In the gate, Zuul will clone the latest master from
+# placement OR the version of placement the Depends-On in the commit message
+# suggests. If you want to run the test locally with an un-merged placement
+# change, modify this line locally to point to your dependency or pip install
+# placement into the appropriate tox virtualenv. We express the requirement
+# here instead of test-requirements because we do not want placement present
+# during unit tests.
+deps =
+  -r{toxinidir}/test-requirements.txt
+  git+https://git.openstack.org/openstack/placement#egg=openstack-placement
 commands =
   {[testenv]commands}
 # NOTE(cdent): The group_regex describes how stestr will group tests into the
@@ -93,15 +107,15 @@ commands =
 # with python 3.5
 [testenv:functional-py35]
 basepython = python3.5
-envdir = {toxworkdir}/py35
 setenv = {[testenv]setenv}
+deps = {[testenv:functional]deps}
 commands =
   {[testenv:functional]commands}
 
 [testenv:functional-py36]
 basepython = python3.6
-envdir = {toxworkdir}/py36
 setenv = {[testenv]setenv}
+deps = {[testenv:functional]deps}
 commands =
   {[testenv:functional]commands}