Project.api_destroy(): optional user to perform the call

As the updated example in `test_projects` shows, there are cases
where the project owner doesn't really has enough rights to do so.

--HG--
branch : oldstable
7 jobs for !88 with topic/oldstable/external-user-bumped-quota in 18 minutes and 53 seconds (queued for 1 second)
latest detached
Status Name Job ID Coverage
  Lint
passed flake8 #197922

00:00:14

 
  Test Heptapod
passed docker-inside #197923

00:18:39

passed docker-native-inside #197926

00:18:26

passed docker-native-remote-0 #197927

00:17:21

failed docker-native-remote-1 #197928

00:16:45

passed docker-remote-0 #197924

00:14:39

failed docker-remote-1 #197925

00:17:44

 
Name Stage Failure
failed
docker-remote-1 Test Heptapod
-- Docs: https://docs.pytest.org/en/stable/warnings.html
=========================== short test summary info ============================
FAILED tests/test_instance.py::test_admin_views - AttributeError: 'User' obje...
================= 1 failed, 11 deselected, 1 warning in 3.27s ==================
ERROR: InvocationError for command '/builds/heptapod/heptapod-tests/.tox/py3/bin/py.test --lf -v --num-shards=2 --shard-id=1 --heptapod-url http://172.17.0.5 --heptapod-ssh-port 22 --heptapod-remote --heptapod-webdriver-remote-url http://selenium-1:4444/wd/hub' (exited with code 1)
___________________________________ summary ____________________________________
ERROR: py3: commands failed
Cleaning up file based variables
ERROR: Job failed: exit code 1
failed
docker-native-remote-1 Test Heptapod
-- Docs: https://docs.pytest.org/en/stable/warnings.html
=========================== short test summary info ============================
FAILED tests/test_instance.py::test_admin_views - AttributeError: 'User' obje...
================= 1 failed, 11 deselected, 1 warning in 2.68s ==================
ERROR: InvocationError for command '/builds/heptapod/heptapod-tests/.tox/py3/bin/py.test --lf -v --num-shards=2 --shard-id=1 --heptapod-url http://172.17.0.5 --heptapod-ssh-port 22 --heptapod-remote --heptapod-webdriver-remote-url http://selenium-native-1:4444/wd/hub --heptapod-hg-native' (exited with code 1)
___________________________________ summary ____________________________________
ERROR: py3: commands failed
Cleaning up file based variables
ERROR: Job failed: exit code 1