Skip test_get_instance_action test for nova v3

InstanceActionsV3Test.test_get_instance_action() relies on the
x-compute-request-id header existing in the response from create_test_server()
in setUpClass(). That header name is going to be replaced for nova v3,
pending change I5e370fd3de5ee2f8a8d13553015d88910ff5ea87

So for now, skip that test in v3. The header name can be updated after the nova
change merges.

Change-Id: Ia1880dd53b7cbf34e66b349f01afb15672dffd12
Revert "always use sitepackages"

This reverts commit c81568fa85620746534331cd820b0bb399719149.

After learning what I learned about how sitepackages works, this
wasn't really a sane change. Revert back to old behavior.

Change-Id: I8079a0f4d9e0bc2e51a743d4f23cf98d4840a3ab
Merge "Skip test_get_instance_action test for nova v3"
Merge "Revert "always use sitepackages""
Merge branch 'master' of https://github.com/openstack/tempest