We had this library capped at a release that is a few years old. Now
that we have dropped py2 testing, we can pick up the latest version.

This uncovered a few things to clean up. Mostly the fact that mock is
now a part of the StdLib unittest since Python 3.3.

Change-Id: I27484dd4c25378413ff16e97a35a1a46062357bc
Signed-off-by: Sean McGinnis <sean.mcginnis@gmail.com>

python-novaclient 16.0.0 removed the deprecated
list_extensions module [1] so this changes the
extensions command to use openstacksdk to get the
compute API extensions.

The functional test ExtensionTests.test_extension_list_compute
ensures this works.

[1] https://review.opendev.org/686516/

Change-Id: I9894bc395c0474aaa6494ac4534862efe4ea7984
Story: #2006769
Task: #37284

1.keep the column display order consist in extension list with
  and without "--long" option.
2.rework for network extentsion list, openstacksdk return object,
  so the logic should be same with other service.
3.add some unit test cases, like: extension list --network --long,
  extension list --network --compute, to cover regular use cases.
4.raise exact exception when network extension don't exist, avoid
  internal TypeError in "extension show" commands.

Change-Id: I2e23ced80d8da8aa1106b22472db850367b351ce
Closes-Bug: #1689233

Implement Neutron feature of Extension Show into
OpenStack Client.

Change-Id: Ifecb794838cb3bf8c2466d178345349db3cd4003
Implements: blueprint extension-show

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