Clarify snapshot deletion methods

There are two similar and confused things presented in code:
'handle_delete_snapshot' and 'handle_snapshot_delete'. In this patch
documenatation is updated to clarify current differences between this
two features.

Change-Id: I88997df97956cc36b071f116dd678df109e0f2de
Adding tests for sahara client exeptions

Currently sahara client has not any tests for common methods. This patch
adds missed tests and also sets exceptions_module variable.

Closes-bug: #1380563
Change-Id: I6b9482f585847ff32a1ca71ba383a19a33b6bddf
Make Rackspace Cloud DNS TTL constraints match API

The Rackspace Cloud DNS TTLs have a minimum constraint of 301, but,
according to the API docs, the minimum is "300 seconds or more".

Change-Id: I924889f859de4226d5e7517576e40d1fdbba3064
Closes-Bug: #1380755
Add tox genconfig target

It's easy to get a false config generated using a local (non venv)
environment to run generate_sample.sh, so this makes it easier to
run the config generator in a venv for consistent results which
should match what's done in the gate.

Possibly in future we could consider removing the static conf.sample
like some other projects have already done and just documenting
this as the method to generate the sample.

Change-Id: I92964d75e0adf73eb0935c2052adf344f15bfe95
Remove unused oslo lockutils module

This isn't specified in openstack-common.conf and is unused,
so remove it.

Change-Id: Iff88b6b68b9c9c739e96f4bf6a9de83e4c4de812
Partial-Bug: #1380629
Merge "Clarify snapshot deletion methods"
Merge "Make Rackspace Cloud DNS TTL constraints match API"
Merge "Adding tests for sahara client exeptions"