Change pyrax identity_type of Rackspace resources

The Rackspace resources utilize the pyrax library. As of v1.4.11 of
pyrax, the manner in which default region is determined changed, such
that the keystone identity_type returned 'RegionOne' as the default
region rather than one of the Rackspace regions. Changing the
identity_type to rackspace fixes this.

Change-Id: I36cd61393a76fbb9b0bb1fd4b31f26f6a95df3a3
Closes-Bug: 1227387
Make the testing of resource loading easier

Pass an environment object around so tests don't have
to use the global object and then conflict with other tests.

Change-Id: I0d9a0d3bd825ac415847213ee4a5d7473f80dbd6
Partial-bug: #1236107
Move the registration of the global env to after plugin resources

This prevents a user's template resources from getting overridden
by a resource plugin.

Change-Id: Idd1a5155dd28d662df8cdc44d190e24c84fd7a81
Closes-bug: #1236107
Cleanup nested loop variables in TemplateResource

This patch makes these variables more verbose.

Change-Id: I40d6d3d2b0ffc9d792c75de51b5107e5fa73bd91
Partial-bug: #1235077
Don't try validate TemplateResource properties in template_validate

If the user runs "heat template-validate ..." and one of the resources
is a TemplateResource we won't be able to validate the properties
of that resource as we have to instantiate the TemplateResource
to kick off downloading the template and conversion of parameters to
properties.
Note: validation will happen properly when the user creates the stack
      so this just delays the validation of one resource type by one step.

Change-Id: I6ce53a9e78ae470b54320862fe910eef9f603941
Closes-bug: #1236327
Update some cases of iterating stack resources

Since https://review.openstack.org/#/c/49879 iterating over a
stack will return resource names instead of resources.

This change updates some cases of iterating on a stack, there
are likely others which remaint to be updated.

Change-Id: I3fff5d7d7fd0016d741151010d0e1ce969da01b3
Partial-Bug: #1236678
Don't install EPEL rpm on CentOS 6.4

Attempting to install the already-installed EPEL rpm on CentOS 6.4
causes stack-create to fail.

Change-Id: I0474622e3976113ec3b80855f3a04a3e339ab193
Merge "Update some cases of iterating stack resources"
Merge "Cleanup nested loop variables in TemplateResource"
Merge "Don't try validate TemplateResource properties in template_validate"
Merge "Make the testing of resource loading easier"
Merge "Move the registration of the global env to after plugin resources"
Merge "Change pyrax identity_type of Rackspace resources"
Merge "Don't install EPEL rpm on CentOS 6.4"