neutron: change default credentials for nova notifications

By default, we should use "admin" tenant to get an admin token and make
the VM connectivity working in Nova.

Using Nova user will fail since Nova (services tenant) can't get an
admin token.
Use ensure_resource instead of create_resources

create_resources doesn't allow to pass array of values but a hash.
Which prevent it from working as we expect.
neutron: revert some changes for nova notifications

It seems we need to use "services" tenant to send notifications to Nova
API, using Nova user.
Remove redundant realization of ring_*_device

Since they are already realized in swift::ringbuilder, it is not necessary
to realize them here.
Bump puppet-swift version

Bump puppet-swift version to a version that supports ringbuilder and
storage node to be installed on the same node.
Replace the formatter in the rspec SPEC_OPTS

TravisCI does not seem to enable the 'n' formatter anymore, hence
we use the documentation one.
Merge pull request #481 from enovance/nova-notifs

neutron: revert some changes for nova notifications
Merge pull request #484 from enovance/fix_invalid_parameter_issue

Apply changes for swift to compile
Force travis/spec to use RSPEC version 2.14.x

Since our test are not rspec 3.0.0 ready, we need to force travis
to use rspec version 2.14.x
Merge pull request #485 from enovance/change_rspec_formatter

Replace the formatter in the rspec SPEC_OPTS
compute: allow more granularity on hypervisor nodes

- Allow to enable / disable RBD storage for:
  * Instances & Volumes
  * Volumes only (instances will be stored locally then)
- Deprecate has_ceph param with backward compatibility
- If RBD backend for instances is enabled on Red Hat, fail with a
  message.

Closes-bug #486
Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>