Use six to make dict work in Python 2 and Python 3

Dict's interface changed a lot between Python 2 and Python 3.
Use six to make dict work in them.
This is mapping:

six            Python 2        Python 3
six.iterkeys   dict.iterkeys   dict.keys
six.itervalues dict.itervalues dict.values
six.iteritems  dict.iteritems  dict.items

Part of blueprint keystone-py3kcompat

Change-Id: If41b19353f07853e39064f848ba74e9cdfd9bd14
Fix typos in documents and comments

Fix typos detected by toolkit misspellings.

* pip install misspellings
* git ls-files | grep -v locale | misspellings -f -

Change-Id: If986f8cfefae08089caa567618dbb13bff0d62d2
Cleanup eventlet setup

Since environment.use_eventlet() is done in test/core.py, no need
to also do it in fixtures/appserver.py

Change-Id: I1bb4ebbca7a423ab30d945745e092cadf8817da6
Fix reading cache-time before configured

There were several places where the cache time was read at
import-time. This means that the default value is used rather
than the value that the user configured because CONF() had not
been called yet.

This change makes it so the values are read at run-time, after
CONF() has been called.

Change-Id: I835418f249c5217bf79efebad1dee22d25f6774a
Closes-Bug: #1265670
Don't configure on import

The keystone.config package called config.configure() at import-
time.

This will make it obvious that developers can't use config
options at import-time because packages that do that will fail on
import.

Change-Id: I9306f67609d782e3f49fd43908448daf1287d51c
Related-Bug: #1265108
Related-Bug: #1265670
Closes-Bug: #1269785
use assertEqual instead of assertIs for string comparison

Change-Id: I83fd4c28007e5242b69d2473d4a91f6801c49601
Merge "Fix reading cache-time before configured"
Merge "Don't configure on import"
Merge "Fix typos in documents and comments"
Merge "Cleanup eventlet setup"
Merge "use assertEqual instead of assertIs for string comparison"
Merge "Use six to make dict work in Python 2 and Python 3"