Add console_urls attribute to server resource

This is a composite attribute that returns a dict-like structure
lazily resolving the actual console URL based on key supplied or dict of
all available consoles if no key is provided.
Example of usage to get only 'novnc' console:

  outputs:
    console:
      value: { get_attr: [server, console_urls, novnc ] }

Change-Id: I27c0426f1a9100bb483f04c059fec87bb69b6340
Implements: blueprint vnc-console-attr
Co-Authored-By: Jun Jie Nan <nanjj@cn.ibm.com>
Always import heat.rpc.api as rpc_api

heat.rpc.api was being imported as rpc_api in some modules and engine_api
in other modules.  Always import heat.rpc.api as rpc_api for consistency.

Change-Id: Ic84ca7fbac7a95eace7f2019c08ee20fa1bc8e5e
Use the right log marker functions

According to [1] _LI() should be used for LOG.info(), _LE() for
LOG.exception() and LOG.error(), _LW() for LOG.warning().
The log marker functions must only be used when the message is
sent directly to the log.
Debug level log messages should not be translated.

[1] http://docs.openstack.org/developer/oslo.i18n/guidelines.html

Change-Id: Ib9f92ef6696b9a95ddae74f0d4a0a557c06ecc91
Add cinder volume custom constraint

Add cinder volume custom constraint to validate
the existent of the volume not wait creation.

Change-Id: Idf4b7139eff2532e71aff48ff4a965c9e52a0921
Implements: blueprint cinder-custom-constraints
Support better access to nested attributes

This makes it easier to get access to attributes  with in
a nested stack.

bp env-nested-usability
Change-Id: I047794906ae7eb3b72b6cc779c64a9ba6e73e68a
Revert "Handle error with non existing template file"

This is causing the test_stack_update_provider_group functional test
to fail, so revert while we investigate.

This reverts commit 51390e8ba70cc22202e27f972455af66d3dbe779.

Change-Id: I271780f3ac02030dfde9ba9beb8921dc9211c06d
Merge "Add cinder volume custom constraint"
Merge "Revert "Handle error with non existing template file""
Merge "Use the right log marker functions"
Merge "Support better access to nested attributes"
Merge "Always import heat.rpc.api as rpc_api"
Merge "Add console_urls attribute to server resource"