Add an option to enable version 1.0 of the AMQP messaging protocol

This change adds the RPC_MESSAGING_PROTOCOL configuration option that
selects the messaging protocol that is used by the RPC backend and
client.

Some brokers can support different kinds of 'on the wire' messaging
protocols.  Qpid, for example, supports both AMQP 0-10 (the default),
and AMQP 1.0.  Use the RPC_MESSAGING_PROTOCOL configuration variable
to override the default protocol for those brokers that support
multiple protocol options.

This new option is necessary in order to enable the new AMQP 1.0
oslo.messaging transport as described in the blueprint.

Note well: currently this AMQP 1.0 functionality is only available on
fedora 19+ platforms.  Support is WIP on ubuntu/debian and rhel/centos
7. Enabling the RPC_MESSAGING_PROTOCOL option on an unsupported
platform will cause devstack to exit with an approriate error
message.

Change-Id: Ib8dea59922844e87d6c947b5dca557f5b5fc1160
Implements: blueprint amqp10-driver-implementation
Split keystone mod wsgi config from start/stop

We currently cleanup keystone apache config during stop_keystone
when mod wsgi is enabled, but only create it during initial keystone
configuration.  Grenade expects to be able to stop and start the
service without reconfiguring it, using only the respective functions.
This moves cleanup of config from stop_keystone to cleanup_keystone,
and enables/disables the apache vhost during start/stop.

Closes-bug: #1365105

Change-Id: I9e57c9a763fbdb8c5737decfe797ba0e9894150b
Merge "Add an option to enable version 1.0 of the AMQP messaging protocol"
Merge "Split keystone mod wsgi config from start/stop"
Merge branch 'master' of https://github.com/openstack-dev/devstack