Remove "node" parameter from methods handling power state in docs

This patch fixes the doc about methods handling power state
to remove the parameter "node".
* validate
* get_power_state
* set_power_state
* reboot

Change-Id: I5c0425e1502f304b62566aa1e63823214888ef66
Partial-Bug: #1312632
Pass kwargs to ClientWrapper's call() method

As the ClientWrapper class had no unittests some were added to test
the specific part of the code for this change. The FakeClient() and
associated classes from test_driver.py were moved to a common file to
make it easier to be imported and used by the new unittests.

Partial-bug: #1316549
Related-bug: #1309719
Change-Id: I11be25a6ce981e63027073d12fbf2922896f4693
list_instances() to return a list of instances names

Previously the list_instances() method in the Nova Ironic driver was
returning a list of instances UUIDs instead of a list of instances names
causing various checks throughout nova.compute.manager to always return
False for Ironic.

Closes-Bug: #1309719
Change-Id: I0ed29911f180f99a7e2b1c00ddd6c43064f04f7f
Merge "Remove "node" parameter from methods handling power state in docs"
Merge "Pass kwargs to ClientWrapper's call() method"
Merge "list_instances() to return a list of instances names"