This moves out the engine next to run (or revert)
selection process to a single class that just does
this and moves out the common functions the analyzer
class provided to the runtime object (which all
components can access).

This makes it easier to adjust the selection algorithm
in different ways.

Change-Id: I091c69297a7bff60729791d3ca6c3fae14d6eea5

Trivial fix

[H106] Don't put vim configuration in source files (off by default).

Change-Id: I7e9e9930fd6f135074078637f5af6f403e75ff78

[H203] Use assertIs(Not)None to check for None (off by default) Unit
test assertions tend to give better messages for more specific
assertions. As a result, assertIsNone(...) is preferred over
assertEqual(None, ...) and assertIs(None, ...), and assertIsNotNone(...)
is preferred over assertNotEqual(None, ...) and assertIsNot(None,
...). Off by default.

Trivial fix

Change-Id: I5b6ac7d99f0689843eb98cb3e9b9b10531322640

http://docs.openstack.org/developer/taskflow/utils.html points to
http://docs.openstack.org/developer/taskflow/kazoo.readthedocs.org/ -
fix the broken URL.

Change-Id: I6f6650cef94cea9d6f138925e5e8d2ed6ea177c3

This patch replaces the legacy retrying library with the newer
and more convenient tenacity one, taking into account that:
1) retrying uses milliseconds for wait times, but tenacity uses seconds;
2) retrying has a lot of numeric arguments for specifying behaviour
of decorated functions, while tenacity has a few of them, which are
specialized objects, thus making the retry-decorator more flexible.

Change-Id: I4b165d37b2ecc210f2b94c103b73eaab51529261
Closes-Bug: #1635404

Following OpenStack Style Guidelines[1]:
http://docs.openstack.org/developer/hacking/#unit-tests-and-assertraises
[H203] Unit test assertions tend to give better messages for more
specific assertions. As a result, assertIsNone(...) is preferred
over assertEqual(None, ...) and assertIs(..,None).

Change-Id: I52ecf3f4945c4cb99f6350afca1c51d88b16bb8d

TrivialFix

Change-Id: Idc9498e7697844fa42a8688880c026b36e60ed93