Test for remote directory creation before shutting down instance

This patch moves the creation of the directory on the migration target
earlier in the code path so we can catch failures like missing or incorrect
keypairs on the source and destination node.

This fixes part of bug #1061024 but not all of it yet.

Change-Id: I097cf007cdd8de0c9c3a9390cbc6dc202eddb2b5
Remove path_exists from NFS/GlusterFS drivers

mkdir -p will not throw an error if the path already exists,
so this method is unneeded in these classes.

Change-Id: I65a67cb75f83f65a6f80c7a90f77c2c5133bd41b
Fix log message.

Fix a missing key in the log format.

Change-Id: I275f5e5fbfb6465b39d9ed7b4a9ace045ded4b5d
fix a misleading docstring

GroupAntiAffinityFilter was introduced to filter a set of hosts,
howerver the docstring saying filter a set of instances which need to be
fixed.

Change-Id: Icf66a3ad15b4135c06e2e2ccc62837a346fcfdf7
Fix and enable flake8 F812

F812 list comprehension redefines

List comprehension don't have scope so redefining variables can lead to
unexpected behaviors

Change-Id: I85484dfcd4fa391195ea7be75aadc7897da4739c
Fix and enable flake8 F823

F823 local variable 'blah' (defined in enclosing scope on line xx)
referenced before assignment

Change-Id: I721e1339ef023558032980bbf59e8dc44b391d52
Enumerate Flake8 E12x ignores

Instead of ignoring all E12x errors, ignore only the failing ones,
so its easy to fix each one separately.

Change-Id: Id365f4d61be56b51823ead8c7c1948e034ea609b
Add posargs support to flake8 call

Add posargs to flake8 call in tox.ini, with this you can pass arguments
directly into flake8 using the following notation
  tox -epep8 -- --FLAKE8-ARG

Change-Id: I1296eac3df46438ef050bf99ca33eb38d3b02efa
Cell weighing class to handle mute child cells

Give negative weight to child cells that have not recently sent
capability or capacity updates to their parent cell.

Change-Id: I7cada3e1b6f04c48b71c82d8e0a8527e44674abd
Add update method of security group name and description

make it possible to edit the name and description of
common security groups, we can not rename the default.

Fixes: bug #918393

Change-Id: Id6e02cd1054452889282b3ff4fb04b2071980cc8
Merge "fix a misleading docstring"
Merge "Fix log message."
Merge "Fix and enable flake8 F812"
Merge "Cell weighing class to handle mute child cells"
Merge "Fix and enable flake8 F823"
Merge "Enumerate Flake8 E12x ignores"
Merge "Add posargs support to flake8 call"
Merge "Test for remote directory creation before shutting down instance"
Merge "Add update method of security group name and description"
Merge "Remove path_exists from NFS/GlusterFS drivers"