Check that personality is provided before iterating

Change-Id: I3453dee8ce3ec1fd7fba9de16c82f9a6788a7be2
Closes-Bug: #1324619
Remove optional imports from clients.py

Why:
- These are in the requirements
- Heat is now well down the path of been a part of the integrated release
- All of the above clients are also integrated.
- If someone wants to use heat on an old OpenStack they still can
  as long as they install the required recent client libraries,
  which are backwards compatible with older OpenStack releases.

Change-Id: I39d7dcbd3e5655d3da1c97de5ff7eceb1826d4ea
Fixes-bug: #1174005
Move Engine initialization into service start()

Currently we create the ThreadGroupManager and EngineListener
objects in the service constructor, which is not necessarily
going to work if multiple worker processes are specified in
the config file (which fork multiple workers after the constructor).

The ThreadGroupManager appears to work, even when it is created before
the fork, but this is due to some magic in the oslo ProcessLauncher
implementation which decouples parent/child use of the eventlet hub.

So instead, we move all service startup code into the start() method,
which is the entry point for services, triggered via the oslo Services
class run_service method:

- Don't create anything common to the workers in the constructor
- Move ThreadGroup and EngineListener creation into start()
- Create the periodic tasks from bin/heat-engine, which means
  the periodic tasks will only be created by the parent, not
  duplicated in every worker process.

These changes should mean we work correctly with both the ServiceLauncher
(num_engine_workers==1) and ProcessLauncher(num_engine_workers>1) oslo
abstractions, and solves the issues observed when running multiple
workers with the impl_qpid rpc_backend.

Change-Id: If3a11050a03660560a364dec871f85c4b56c1c25
Closes-Bug: #1321303
Merge "Check that personality is provided before iterating"
Merge "Move Engine initialization into service start()"
Merge "Remove optional imports from clients.py"
Revert "Use auth_token_info to initialize heat_keystoneclient sessions"

It looks like this change has revealed an unrelated race with locking
during delete. While this issue is investigated then this change
needs to be reverted to fix the gate.

Related-Bug: #1306029

This reverts commit 535dd4e77e2c439a8611f27e5e9fa821cc8d7589.

Change-Id: I06be473d7c6961e399c4fd6128f374d24b9b0510
Merge "Revert "Use auth_token_info to initialize heat_keystoneclient sessions""