Do a dummy import to determine which SDK is installed (Pre/post merge).

This solves the DevStack error "Cloud defaults was not found" in -tips jobs.

Depends-On: Ia111f127fbdceac2afe20fd9d1fe032145cdd72c
Change-Id: I60c2d418dd5a393eee2cc2a5c2fdebfffdabf2d3

In reviews we usually check import grouping but it is boring.
By using flake8-import-order plugin, we can avoid this.
It enforces loose checking so it sounds good to use it.
This flake8 plugin is already used in tempest.

Note that flake8-import-order version is pinned to avoid unexpected
breakage of pep8 job.

Setup for unit tests of hacking rules is tweaked to disable
flake8-import-order checks. This extension assumes an actual file exists
and causes hacking rule unit tests.

Change-Id: I12b596820727aeeb379bee16c2bc993dee9eb637

[breakage related to os-client-config 1.28.0]
os-client-config 1.28.0 add a check if filebased and envvars are
both used. This check causes OSC unit test failure.

OSC now instantiates OpenStackConfig twice as a workaround.
The unit test mocks _load_config_file() and it returns a config dict,
but os-client-config OpenStackConfig.__init__ updates the dict returned.
As a result, when OpenStackConfig is instantiated second time,
the mock of _load_config_file returns a modified version of the config
dict. This hits the new check in os-client-config 1.28.0.

This commit changes the mock to use side_effect rather than return_value
to ensure the original dict is used.

[breakage related to osc-lib 1.7.0]
The change in osc-lib 1.7.0 added "if" logic to avoid calling get() twice.
In tests.unit.volume.test_find_resource, kwargs is empty dict in find_resource(),
so the second call to get() is NOT called now.
Removing the second elements of side_effect addresses the unit failure.

Co-Authored-By: Rui Chen <chenrui.momo@gmail.com>
Change-Id: Ib9d14661b2755bbd6619e15c0d9023fbc9d27d70
Closes-Bug: #1703782
Closes-Bug: #1703783

this will better isolate the unit tests from the functional tests.
unfortunately, the "integration" tests had to be lumped into the
"unit" tests since we need the separation in testr.conf

Change-Id: Ifd12198c1f90e4e3c951c73bfa1884ab300d8ded