Remove our custom test base class

Nothing is using the features of the test base class, so remove it and
use oslotest directly to make moving tests out of the incubator easier.

Partial-Bug: #1371700
Change-Id: Ifcde81ade9f9954c596e3b5f95c6cbcb258297ba
Remove graduated config modules

We have moved the config fixture with one in oslo.config and replaced
the config generator with a new app in oslo.config.

Change-Id: If15b77d31a8c615aad8fca30f6dd9928da2d08bb
Closes-Bug: #1371708
Remove code that moved to oslo.i18n

Remove the modules that went to oslo.i18n and their tests, then update
the other modules and tests to use oslo.i18n.

There are a few cases where other modules that will be deleted from the
incubator for juno had references to gettextutils, especially for their
tests. These are commented out as an expedient way to make the tests
run, in anticipation of the files being removed separately.

Change-Id: Ib80a3f0b0f6e96065e86a9b477aebd8bce1201ba
Closes-Bug: #1371702